Database Users

Soft-Bricked S4 by Flashing Different Version Rom

Hi everyone,
Before blasting away with comments as to why I would do this, here's my story,
I live in Canada and just brought home a i9508, a China variant of the S4. It belonged to my dad and he didn't want it so I just took it. The i9508 doesn't have Play Store, and it doesn't work on Canadian 3G network.
So to me, the phone is useless right off the start (don't intend on selling it either, who wants it?) So I had 2 options:
1) Leave the phone as it is, and probably use it once every 1-2 years when I visit HK
2) Flash custom roms on it fully aware of the risk it will have so that there's a possibility I can make it more usable
So in the end I went with option 2.
I followed a guide and flashed TWRP for i9505 using Odin onto the phone, and used TWRP to install chainfire SU, and it actually worked (but SU wouldn't open because some sort of security on the phone is blocking it)
Next step, I downloaded the CM version for i9505 and flashed onto the phone, and that worked too. Only problem I've encountered was that the phone would only boot after a fresh install. If I installed CM, turned the phone off after the initial start up, the phone wouldn't boot pass the Samsung logo.
Up until this point, I didn't make a backup, because of my arrogance, cause I have available a copy of the official firmware, in case anything happens.
So I figured at this point, maybe if I restore the original firmware, and try the whole process again, the custom rom would work. So I went into Odin, flash the firmware with PDA, and failed. It just wouldn't work. After retrying it a couple of times, and downloading different updates of the firmware, nothing worked. Only thing working right now is, I can get into Download mode, and I can get into TWRP recovery (but for some reason, I can't flash the zips that I've adb pushed onto the phone, zip can't open)
For me, if it can't be fixed, then it's really SOL. But if there's a way to fix it, I'm open to testing anything people have in mind, cause afterall, this phone is paper weight either way. I'm interested in seeing if I could enable 3G by flashing a i9505 radio, despite warnings, although, I've never actually came across a thread where someone had actually tried it before.
Either way, if someone has any idea on how to fix the phone, and wouldn't mind sharing it, that'll be greatly appreciated.
Working
I can get into Download mode, but Odin is failing (if you need the error please let me know and I'll post it)
I can get into TWRP recovery, but can't flash files
I can get into adb

This isnt the correct forum for your phone. XDA don't follow clones

Unfortunately a section for i9508 doesn't exist, so I figure the closest one would be i9505.
Anyhow, if someone has an idea of how to fix it, I'm more than happy to do testing on it, like flashing other roms or radios.

Note 4 Stuck in Boot Loop - Help - Recovery not working - Flash stock Rom not working

Note 4 Stuck in Boot Loop - Help
I have a Note 4 SM-N910F, never been rooted, stock rom upgraded to 5.1.1 back in October, working fine until yesterday when it got stuck in a Boot loop.
Not sure what caused it but before it got stuck I was messing around with Google Photos which was running a bit slow.
Also I put it on the Qi Charger just before the loop started. It has an aftermarket Fone charger stuck to the battery. I’ve had this and the Qi Charger for 6mths with no problems before now.
It gets to the Samsung page waits a couple of seconds then boots again.
Here’s what I’ve tried - unsuccessfully - to fix the boot loop:
1: recovery mode.
I can get the little recovery text to appear in the top left but after a few seconds it boots again.
2: volume down, home
This gets me to the screen with up/down for continue/cancel.
This is the _only_ screen I can get to stay up without rebooting. It sits there waiting for input.
- Cancel, causes restart, of course, but back into the bootloop
3: Mashing on power button. Banging it, wiggling it, blowing on it.
I read somewhere this could cause a boot loop, but I doubt it is my case because
a. I’ve never had problems with the power button before
b: When I take out the battery and put it back in, it does NOT turn on. If I do the same holding the power button, it powers into the boot loop. So if the button were jammed on I would expect it to never remain off with the battery in.
3: flashing stock rom
I’m not 100% sure what build I had before. I know it was stock 5.1.1 OTA, and I’m pretty sure it was unlocked (my wife bought the phone and i inserted my old sim, but she may have bought it from my carrier and can’t remember)
So anyway I tried all three versions of TPH (unlocked) 5.1.1 from Sammobile.
Installed Odin 3.10.7 and flashed them.
It reboots to recovery but immediately boot loops again.
I doubt its to do with the version of the rom anyway since the symptoms are identical after flashing. Only now the boot loop always shows the little ‘recovery booting...’ text in the top left.
Here’s what I have NOT tried but am thinking about:
A: Re-partition option in Odin
B: Nand Erase All option in Odin
C: Buying a new battery.
On A/B: as far as I can tell what I have done so far should have left the data intact. I’m prepared to wipe all my data if it fixes my phone (no lectures about backups please!) and I’m tempted to do one of these on the off chance that the problem is caused by data or the “disk" problems.
But I don’t want to brick it. Can someone recommend how likely these are to help
And what they actually do?
(Please refrain from responses I see elsewhere like “this will brick your phone if you don’t know what you’re doing”. I don’t know what I’m doing, thats why I’m asking - just the facts please)
On C: the battery seems ok in that the power is solid even after not being plugged in for a long time, but since it was on the Qi Charger with that aftermarket thing stuck to it when it happened, I’m suspicious. Can any one say if this is a likely cause?
If so, it might be worth waiting till I get a new batter before doing A or B (can I wait days for Amazon!?)
[UPDATE] Got a new (genuine) battery at a local electronics store. No dice. Same problem, so it's not the battery. Shall I go ahead and re-partition.
[UPDATE] Got a PIT file from another forum, and flashed again with re-partition checked and PIT loaded. same results.
Is Nand-rease worth trying?
The phone is still under warranty so maybe I can return it.
But in that case I want to erase what's on it first.
thanks for any help
rhubarb

I don't think that the Samsung service center will accept cuz u have unofficiall custom
Simple Go to ur any nearby SOFTWARE ENGINEER may be he will help u out
Even I had the same problem with my NOTE 4 EDGE

Try downloading and flashing any "COJ5" build of 5.1.1 from sammobile. Samsung has recently issued a new update "COJ5" it basically locks down the bootloader and will not allow the device to run any previous builds.....Maybe your phone updated to COJ5 in the background and then it started messing around because the phone is rooted. Flashing "COJ5" will lock your bootloader and you will not be able to flash 4.4.4 or 5.0.2 but there is nothing to lose when your phone is already pretty much dead?.....ORRR if this is not a software issue then it could be related to hardware maybe the memory of your phone is done. I am not an expert on this but this is just an advice.....i have told you what will happen if u flash coj5 build now its up to you to decide. I would suggest you wait and wait if you are lucky to get a response from an expert and do what they say .......if not then give this a try!
**EDIT** another idea....First flash a custom recovery such as TWRP....see if it lets you boot into recovery and if it does then perform all sorts of formats.....and factory resets in there see if it works....if its still rebooting after format then flash the coj5 build of 5.1.1....note that you "MUST" format it with TWRP first and then check if its working because once you have coj5...it might not let you flash custom recoveries.

dork997 said:
Try downloading and flashing any "COJ5" build of 5.1.1 from sammobile. Samsung has recently issued a new update "COJ5" it basically locks down the bootloader and will not allow the device to run any previous builds.....Maybe your phone updated to COJ5 in the background and then it started messing around because the phone is rooted. Flashing "COJ5" will lock your bootloader and you will not be able to flash 4.4.4 or 5.0.2 but there is nothing to lose when your phone is already pretty much dead?.....ORRR if this is not a software issue then it could be related to hardware maybe the memory of your phone is done. I am not an expert on this but this is just an advice.....i have told you what will happen if u flash coj5 build now its up to you to decide. I would suggest you wait and wait if you are lucky to get a response from an expert and do what they say .......if not then give this a try!
**EDIT** another idea....First flash a custom recovery such as TWRP....see if it lets you boot into recovery and if it does then perform all sorts of formats.....and factory resets in there see if it works....if its still rebooting after format then flash the coj5 build of 5.1.1....note that you "MUST" format it with TWRP first and then check if its working because once you have coj5...it might not let you flash custom recoveries.
Click to expand...
Click to collapse
You can flash TWRP through ODIN while on COJ5 bootloader. It's locked but you still can flash recoveries and kernel and 5.1.1 ROMS

I am very interested in this thread. I have the EXACT same problem as you have after installing SimplRom, which was a ROM prior to COJ5. It could indeed be that our bootloaders are locked now?
I am using the N910F and just like you, installing any ROM/Custom Recovery/Bootloader/Kernel doesn't help. Perhaps installing a COJ5 ROM might help. I will give that a try, but I've recently used Kies to install the latest official firmware, but it didn't fix the issue.
I will report back here and we'll work on this together to make our phones work again!

Osama lakdawala said:
I don't think that the Samsung service center will accept cuz u have unofficiall custom
Simple Go to ur any nearby SOFTWARE ENGINEER may be he will help u out
Even I had the same problem with my NOTE 4 EDGE
Click to expand...
Click to collapse
Thanks but:
1: I have no custom rom. I have never had a custom rom on this device. I want to take it to Samsung, but want to clear the memory first. How can I do that?
2: I _am_ a software engineer_

dork997 said:
Try downloading and flashing any "COJ5" build of 5.1.1 from sammobile. Samsung has recently issued a new update "COJ5" it basically locks down the bootloader and will not allow the device to run any previous builds.....Maybe your phone updated to COJ5 in the background and then it started messing around because the phone is rooted. Flashing "COJ5" will lock your bootloader and you will not be able to flash 4.4.4 or 5.0.2 but there is nothing to lose when your phone is already pretty much dead?.....ORRR if this is not a software issue then it could be related to hardware maybe the memory of your phone is done. I am not an expert on this but this is just an advice.....i have told you what will happen if u flash coj5 build now its up to you to decide. I would suggest you wait and wait if you are lucky to get a response from an expert and do what they say .......if not then give this a try!
**EDIT** another idea....First flash a custom recovery such as TWRP....see if it lets you boot into recovery and if it does then perform all sorts of formats.....and factory resets in there see if it works....if its still rebooting after format then flash the coj5 build of 5.1.1....note that you "MUST" format it with TWRP first and then check if its working because once you have coj5...it might not let you flash custom recoveries.
Click to expand...
Click to collapse
Thanks to you and dork97 for the ideas. First some notes:
- I have never flashed a custom ROM, nor ROOTed this Note 4. The recent upgrade to 5.1.1 was official.
the first upgrade to 5.0.1 was automatic and after that I turned off automatic upgrades and upgraded to 5.1.1. manually. So I dont think it was an upgrade that caused it and it certainly was NOT a custom ROM or ROOT. I was doing nothing at all when the boot loop started.
- I'm not sure what ROM I had, but when I went looking for the available Portugal unlocked ROM, which _should_ be what I had, the latest were CJ03 (3, not 5) and before that CH03, CI03. Presumably I had one of those (my last update was October, so probably CH03).
I have tried all 3 of these, but the symptoms are the same.
I'm tempted to try the TWRP option - but would like some more details on what is and what it does, or what problem I might have that it would fix.
However I am probably still in time for a warranty repair - especially since I didnt actually do anything for this to happen. I would like to avoid losing that chance.
If I do take it in for warranty, I'd like to wipe the memory first though. How can I do that?
Finally can anyone actually tell me if the NAND ERASE is likely to help? How does flashing TWRP compare?
I get the feeling in fact, that I have a hardware problem. Especially given there were not software system changes around the time it happened, and given that it loops while trying to boot into recovery mode. In fact the only mode that doesnt constantly cycle is download mode. (Even holding the power button in dl mode does nothing which makes me suspect that, but pulling the battery out and replacing it leaves it off until I press the power button so perhaps not)
Thanks for the replies so far. Any more ideas, details?

roverrhubarb said:
I get the feeling in fact, that I have a hardware problem. Especially given there were not software system changes around the time it happened, and given that it loops while trying to boot into recovery mode. In fact the only mode that doesnt constantly cycle is download mode. (Even holding the power button in dl mode does nothing which makes me suspect that, but pulling the battery out and replacing it leaves it off until I press the power button so perhaps not)
Click to expand...
Click to collapse
I have the exact same as you. I did install a custom recovery (multiple) and still get the bootloop. From my tries yesterday, I indeed also suspect it may be a hardware issue. Perhaps to do with the battery/charging port. When I have my device unplugged and try to start in recovery/normalboot, it does not have a bootloop but simply turns off (and then doesn't respond until I pull the battery out). I think a NAND erase wouldn't do anything as I've personally tried that already.
Have you prior (upto a week) before you got the issues had your phone in a moist environment (bathroom while showering for example). I got my problems a week after I accidentally left my phone in the bathroom and installed custom ROM (which was done earlier and had no issues).
I've read online that it may have caused oxidation on the inside and may need some cleaning/drying with alcohol.
I still hold hope that we just have a software issue as download mode is working fine (apart from the Power off not working unless we pull out the battery).
Anybody have any experience with oxidation on their phone? Perhaps have had a similar bootloop due to hardware failure?

roverrhubarb said:
Thanks to you and dork97 for the ideas. First some notes:
- I have never flashed a custom ROM, nor ROOTed this Note 4. The recent upgrade to 5.1.1 was official.
the first upgrade to 5.0.1 was automatic and after that I turned off automatic upgrades and upgraded to 5.1.1. manually. So I dont think it was an upgrade that caused it and it certainly was NOT a custom ROM or ROOT. I was doing nothing at all when the boot loop started.
- I'm not sure what ROM I had, but when I went looking for the available Portugal unlocked ROM, which _should_ be what I had, the latest were CJ03 (3, not 5) and before that CH03, CI03. Presumably I had one of those (my last update was October, so probably CH03).
I have tried all 3 of these, but the symptoms are the same.
I'm tempted to try the TWRP option - but would like some more details on what is and what it does, or what problem I might have that it would fix.
However I am probably still in time for a warranty repair - especially since I didnt actually do anything for this to happen. I would like to avoid losing that chance.
If I do take it in for warranty, I'd like to wipe the memory first though. How can I do that?
Finally can anyone actually tell me if the NAND ERASE is likely to help? How does flashing TWRP compare?
I get the feeling in fact, that I have a hardware problem. Especially given there were not software system changes around the time it happened, and given that it loops while trying to boot into recovery mode. In fact the only mode that doesnt constantly cycle is download mode. (Even holding the power button in dl mode does nothing which makes me suspect that, but pulling the battery out and replacing it leaves it off until I press the power button so perhaps not)
Thanks for the replies so far. Any more ideas, details?
Click to expand...
Click to collapse
Well if you still have warranty then don't try anything on your own and go for the warranty repairs.

dork997 said:
Well if you still have warranty then don't try anything on your own and go for the warranty repairs.
Click to expand...
Click to collapse
thanks. How can I wipe personal data without voiding the warranty, using odin or kies? Given I canNOT get it into recovery mode, only download mode.

roverrhubarb said:
thanks. How can I wipe personal data without voiding the warranty, using odin or kies? Given I canNOT get it into recovery mode, only download mode.
Click to expand...
Click to collapse
Since you can get into download mode I'd flash firmware through ODIN again after verifying it's correct.
I'm seeing off the sammobile site for the 910F not all are the COJ5 locked bootloader.
Since you did update in Oct you may be on the COJ3. I'd try one of those and see if it works.
If it doesn't work and stops on the sboot.bin file then you have the COJ5

roverrhubarb said:
thanks. How can I wipe personal data without voiding the warranty, using odin or kies? Given I canNOT get it into recovery mode, only download mode.
Click to expand...
Click to collapse
i am sorry i don't know any way to remove personal data other than doing it via recovery. There is an option of "nand erase" in odin it is used while flashing firmware and it wipes everything on the phone but i have never used it (and also don't know whether it can help you or not) ... Senior members kindly help us with this.

Any update to your situation?
very interested as I am in the same situation as you are. Download mode works, recovery+normal boot not. No matter what ROMs/recoveries I install

Same issue I think
I am also in the same situation, although I can enter the recovery mode - home power and volume up - I have tried the wipe cache and then factory wipe to no avail - I have also entered download mode and flashed the stock recovery and even though Odin says pass, it is still in a boot loop. Also when I go to the download screen it has a line saying knox warranty void 0x1(4) does this mean I have voided the warranty even though I only used Odin to flash stock recovery?

Did anyone found a solution
Did anyone ever found a solution to this problem I'm having the exact same issue on a note 4 smn910a

I have a slightly different issue with my Note 4 SM-N910G, wherein am not able to start the phone at all, it is completely dead, if i put the cell phone on charge then also there is no LED on the top but if i connect the device to the PC it does make the connected sound on the PC but Odin is still not able to recognize the device neither kies. I tried draining the power by removing the battery, connected the device to PC without battery and then inserting it but the same problem. Please suggest me any resolution for this dead body am carrying from past few weeks.

hi Op,
did you find any solution for this issue?

Hello all. This is advice to use as a very last resort if you are experiencing the recovery bootloop issue AND you don't have the emmc failure bug. I had the recovery reboot, sudden shutdown with no warning, etc. issue for the past two weeks. I tried everything on Google and Youtube to fix my problem with no success. I flashed multiple stock ROMS and recovery tars (stock and TWRP) via ODIN, but nothing worked. Oddly enough, I never received the emmc error that I have read about. Also, in the few times that my phone booted normally, I even loaded the Wakelock Power Manager app, set it to partial wakelock and my phone STILL continued to bootloop. As a last resort, I bought a new battery, but the reboot problems continued in Android 4.4.4 Kitkat, 6.0 Marshmallow, 7.1 Nougat and 8.1 Oreo ROMS. Well, here is what finally helped me to get my phone back operational. I had a backup ROM from a previous install and a TWRP flashable version of the same ROM on my SD card (in case the phone did not stay on for the full restore). I put the phone into a ziplock bag into a freezer for about 20 min. (thankfully this time TWRP stayed on long enough for me to do the following):
1) copy all the files I wanted to save from internal storage to a computer.
2) performed a full wipe (Dalvic, Cache, System, etc. Like when flashing a ROM, but this time also internal storage. Note: Please do not wipe both internal and SD card, as you may have a difficult time trying to load the ROM file back on the sd card (assuming you don't have a card reader).
3) After wiping, I was able to restore my stock ROM backup (or you can just flash the stock ROM).
I can't be 100% sure, but I think my wiping internal and then flashing the stock ROM finally did the trick. Since this morning, the phone has been pretty much back to as it was before. In either case, I'm sharing this with the hope that it helps someone else.
Sent from my SM-N910T using Tapatalk

(Soft?)-Bricked My S7 with a Flashfire Update, Need Help to Fix It?

So I've been rooting me phone for a while and have managed to never f*** up, till now, and I sincerely hope you guys can help me.
After rooting my S7 a while back, I just recently noticed SuperUser telling me that I didn't have root anymore, so I decided to follow these instructions to re-root my phone:
https://forum.xda-developers.com/ve...-to-notes-root-install-xposed-unroot-t3411039
I successfully followed all the steps to get root, but when I opened Flashfire it told me I could install a new update while maintaining root, so since my android is at 6.0.1, I did that and it bricked my phone.
On boot it says "Startup Failed - Use the Verizon Software Repair Assistant . . . " and on top it also says "Custom binary blocked by SECURE BOOT." I have tried going into recovery mode and deleting the system cache, but that doesn't do it. So is there any way to get the phone to properly boot while not deleting my data? I was rooting my phone precisely so I could use Titanium Backup again, so I don't have any backups stored anywhere. I have heard that flashing a recovery image with Odin can work, but would that delete my files? Someone please lend me your expertise.
My phone is a Verizon S7.

Fixed
I am surprised that no one responded to me, but what's important is that, miraculously, I managed to un-brick the phone myself without losing any data! What I did was, as my last hope (since Odin wasn't able to flash the stock image, a la the traditional soft-brick fix), decide to follow the on-screen instructions my phone was giving me and to download and run something called the "Verizon Software Repair Assistant," which can be found in the top google results after searching for the quoted name (xda doesn't let me post the link).
After putting my phone into download mode, I plugged it in, ran the software and let it work overnight. Checking on it in the morning, I found my phone, not only completely functional and working, but updated to Android 7.0 (it was 6.0.1 previously before the failed Flashfire OTA update) and still holding all of my data intact.
So, the interesting thing that I learned is that flashing to stock via Odin to fix a soft-bricked phone should not be the default resolution for potentially most people, as the carrier's default (in my case, Verizon's) repair utility managed to completely fix my phone without any side effects or data loss.
Is there anyone who could chime in on why the Repair Utility did not wipe my phone's memory, even though it warned it would?
**Note**
Verizon links to the Windows version of the repair assistant on their site, but to get the Mac version (which I used), the only way you can get it is by changing the end of the url they mention within the thread from "Win" to "Mac."

Pleased you managed to fix it, and thanks for posting the method for others
As for replies, if you stick around XDA you'll see replies can take days sometimes, patience is the key here

*Detection* said:
Pleased you managed to fix it, and thanks for posting the method for others
As for replies, if you stick around XDA you'll see replies can take days sometimes, patience is the key here
Click to expand...
Click to collapse
I guess I am not acquainted with this forum enough then, thanks!

Most likely the cause of the fault would be updating via FlashFire and keeping root. When the update was flashed, it most likely flashed the stock kernel and patched it for root, which is not a compatible root for our devices. Flashing the root kernel with Odin probably would have made the phone boot normally.

Did I just brick my device trying to root?

Hello, I really messed this up... I haven't rooted a phone in over 5 years, but just ordered a moto g7 from google fi because I wanted to play around with rooting and rooted apps again.
Setup:
-got moto drivers, adb, set developer mode, unlocked bootloader
I had tried to just root using the "simple?" method of using Magisk with the lolinet firmware files. I used the PPO files in the Official/FI dir. I thought that I had seen an error when flashing the magisk modified boot.img that there was an issue or that it wasn't valid, I (stupidly) assumed that this was like the notification you get after unlocking bootloader about invalid key or whatever. When trying to boot up it would just keep boot looping, and I went into hard panic mode... I saw other people had mentioned using retail or retus firmware on the google fi variant, so I proceeded to try to just flash those stock boot.img files after the fi one hadn't worked. I then finally got it to boot up fully, I don't even remember which firmware it was (retail maybe) and felt a little bit better about it, but had also seen that some people had said it wouldn't have the full functionality of network switching if I wasn't using the fi firmware. So... back to the fi firmware...
I was able to get it booting up on stock fi firmware, and to be honest I should have stopped there and given up on root, because I'm guessing I would have been perfectly fine up to that point... I again tried magisk modified fi firmware to no avail, and was having trouble getting back on stock fi for some reason... I followed a post to reset to stock and relock bootloader ***I'm guessing this was my major fault***, I must not have been paying enough attention to the command prompts doing this, but I think this is where I messed something up royally. It was able to boot, but then it said it had updated software to the 'PPOS' variant which I thought was strange... After attempting to reflash stock fi and then magisk fi boot.img it is failing and won't even get to boot loop.... when trying the slew of commands to flash full stock firmware I keep getting issues with the "_a" partition being not found.
At this point I can't get to recovery, or boot after attempting to flash a number of times. Any help would be appreciated, even if it is just a confirmation that I f'd this device and to stop wasting my time and give up on ever having a rooted device again lol.
Thanks for your time, and let me know if there is additional info to provide that may help.
Edit: Current status:
"Start Up Failed: Your device didn't start up successfully. Use the Software Repair Assistant on computer to repair your device. Connect your device to your computer to get the software Repair Assistant."
in Bootloader logs, but I don't know what software repair assistant it is referring to, i have tried connecting to pc.
Edit 2: Or I'm just a complete idiot and needed to re-unlock bootloader with the code like previous... which I totally should have known, but again, I'm an idiot...
So, now that I've got it booting up, do I attempt reflashing a magisk img or just admit I'm too stupid to do this? Or should I go with twrp which seemed like more steps and potentially more issues to run into?
Sorry for the scare and immense stupidity!

some basic questions on sm-t235 re: root/custom rom/custom recovery

Hi,
the other day a friend gave me her old Samsung tab 4 7.0 (SM-T235). It's in its default state, running Android 5.1.1 stock ROM with all the most recent (5 year old) updates. "KNOX" appears to be ok, afaik.
This is my first Samsung device, up to the date I had experience with HTC Desire, Sony Xperia (2x) and OnePlus devices. I unlocked / rooted and installed custom ROMs on all of them.
Done quite a bit of googling and playing around with my "new" Samsung to see where it's different compared to my other devices. But there still are some blank spots, and there doesn't seem to be too much information out there regarding that specific tab 4 device. Before I start messing around I'd love to have some input from experienced Samsung users in regards to custom recoveries and ROMs, and possibly rooting. If there are comprehensive guides etc. out there that I simply didn't find don't hesitate to give me some hints:
First of all it appears to me that this device is going under the codename "degas". Correct? (meanwhile confirmed)
I hooked up the device to my PC, made sure that adb found it alright, then called "adb reboot recovery". That worked nicely, got me into Samsung recovery
Next I again tried to connect through ADB to the device still being in recovery, but that didn't work. To be expected?
Still in recovery I chose the "boot to bootloader" option, but that got me back into system instead.
So from system I again connected to adb then called "adb reboot bootloader". Device booted alright, but again it just rebooted into system.
>> Is there really no way to get into bootloader?
Trying to find out what has to be done in order to flash a custom ROM (rooted or not): from what I get, and unlike my other devices, I do not have to unlock the device / bootloader to begin with. It looks as if it was sufficient to boot into what they call "download mode", then hook up the device to my PC where ODIN is waiting already. Following this thread (and others) it then is sufficient to just flash TWRP from ODIN, boot to recovery and then do what is usually done here (like flash custom ROM, flash Gapps and possibly Magisk etc.). Is there something else / important I should know / observe?
Speaking about TWRP and Custom ROMs: TWRP.me lists that device on their site. So has anyone here flashed latest TWRP (3.6.2_x)? Or should I rather start with an older version like the one listed here, then possibly upgrade from there?
In regards to Custom ROMs I basically just found this LOS 16 thread (which is the same linked in the previous "TWRP" bullet). I assume that's it, or does anyone know about a newer android version (which I didn't find so far)? There seems to be lots of activity around "matisse" and "millet", but apparently those aren't the right devices, right?
Back to recovery: I see that in stock recovery there is an option to "wipe data/factory reset": should I do that before flashing TWRP from ODIN, or is it sufficient to wipe everything once I booted into TWRP?
I'm aware that I'll lose "Knox" as soon as I flash a different ROM / Recovery. As I don't want to use the tab 4 in some critical "BYOD" area I don't care (neither do I care about warranty, that's long gone anyways). But just to be sure: is it true that I'll lose "Knox" access?
In case I would decide to "go back" to stock ROM one day, how would I proceed then? Would ODIN still work so that I can flash latest stock ROM? Would Knox then be restored, or is that a thing of the past once I leave the stock ROM path?
Again: if you think I've done a bad job searching for answers don't hesitate to let me know but please be so kind then to hint the phrases I should look for ("SM-T235" really doesn't bring up that much valuable info)
Thanks and cheers
Update 2022-08-03: meanwhile I realized that the device is connected to my PC through generic drivers. Would it help to install specific Samsung drivers although both ADB and ODIN are acknowledging the device? Or can I just neglect that?

Since no answers came in I dared to just try. Meanwhile I'm running the device on LOS 16 with TWRP 3.5.2_9. Then flashed MindTheGapps (arm/Android 9 flavour)The switch wasn't as easy as I expected for some reason not obvious to me (somehow I couldn't get into TWRP after flashing it through ODIN. Then after the ~25th attempt it suddenly worked). Meanwhile I installed the official Samsung drivers, and maybe that helped, in combination with other adjustments I lost trace of...
I'll answer some of the above questions, for anyone who's interested:
#3: while in recovery (TWRP 3.5.2, as it is now) I still cannot access the device through adb. But I have access from windows' file explorer, so at least I can exchange files while being in recovery. Strange thing, this is the only one of my devices that behaves this way. The other day I'll try again from a Linux machine. maybe that works...
#4/5/6: boot to bootloader still doesn't work no matter what I try - devices always boots back into system
#7: Once I managed to get into TWRP the rest was a breeze
#8: I tried TWRP 3.6.0_9-0 which worked but on every boot into recovery it shows first a red notice that recovery was not enforcing SEAndroid. The notice then turns into blue and a second later TWRP logo shows up. This dowsn't happen with TWRP 3.5.2_9, so I stay there for the time being. Then I felt lucky and installed TWRP 3.6.2_9 image from running TWRP recovery, then rebooted. That again showed the red "not enforcing" message - and got stuck there. Solution was to get back into "Download mode" then re-flash TWRP 3.5.2 through ODIN.
Conclusion TWRP 3.6.2 is not fit to be used on that device (no, I didn't try 3.6.1...)
#9: since there aren't any more security updates released by google for A9 ROMs it would really be great to be able to upgrade to an A10 or even A11 ROM... anyone ever tried to use a "matisse" or "millet" ROM?
#10: I decided to use that - wiping everything that was on the device then doing a factory reset as well before flashing LOS 16. Then after first boot into LOS 16 a strange thing happened: when I made a basic setting (in regards to location services" the device told me that in a previous version I had decided to NOT allow google to use those services: after all that wiping and factory resetting: how could the device know that? By that time I had not yet logged myself into Google. Very mysterious!
#11/12: I guess I know the answer: I'm out of "Knox" now once and forever. And apparently ODIN is still working and recognizing the device.
Cheers!