Hey guys, Good news!
If you have a T-Mobile OnePlus 8T, you can convert it to European or Indian firmware, so you can escape T-Mobile stock firmware and get updates, like using the “Local Upgrade” option. My Chat mate on Telegram recently converted his T-Mobile branded OnePlus 8T to European (EU) Firmware without any issues.
Because it’s new, the about phone will show OnePlus 6T picture.
As before, you MUST have sim unlocked and Bootloader unlocked as well by getting unlock token from OnePlus.
Same fastboot ROM method as OnePlus 8.
Also someone just made a Global fastboot ROM as well if you want to use same software as the unlocked 8T model.