Is there any ROMs that have OOS-5 on Oreo from the Oneplus 3/3t to the Oneplus 5?
No, unfortunately.
Just wait, the Android O beta will come this month for OP5
Do they release sources along with the open beta release? or do they release sources only for stable releases?
Been on the beta software for a while and just received Pie 9.0
Yep. Firmware was released the day before your post.
https://forum.xda-developers.com/pr...eak-huawei-hmamate-20-emui9-firmware-t3830921
is possible ????
Most likely no.
I doubt will see an EMUI GSI that works anytime soon, but there's an AOSP GSI of Pie for Kirin devices
https://forum.xda-developers.com/pr...9-0-0-android-p-pixel-features-kirin-t3833879
Is there any possibilities to get treble support after we get pie update on stock?
nah, highly doubt it
no sorry
Can you flash Pie 30a.KDZ if I'm currently running Oreo 20J?
cheers
Matt