Owners of a carrier-branded OnePlus 6T, like the one offered by T-Mobile, may want to switch to universal firmware for personal reasons. This will enable features like dual-SIM functionality, VoLTE. Unfortunately, you cannot receive regular OTA updates.
In this Appuals guide we will show you how to flash the OnePlus 6T to the international firmware if you are on carrier-branded firmware. Follow our steps closely, and comment if you encounter any issues.
- Download the .zip of the full ROM, and extract its contents to your main ADB folder. This means that all of the files to be flashed will be in the same folder as your ADB.exe.
- Now launch your OnePlus 6T into Fastboot Mode (Vol Up + Vol Down + Power) and connect it to your PC via USB.
- Launch an ADB terminal on your PC and make sure the fastboot connection is detected with the command fastboot devices.
- If the connection is recognized, run the flash-all-partitions-fastboot.bat file.
- A terminal will launch on your PC, and ask if you want to wipe all data. If this is the first time you’re converting the device, its recommended to choose Yes.
- The script will do its flashing process, and then say “Press Enter to Continue”. At this point, reboot your OnePlus 6T using the Power button.
Updating After Conversion
Do not flash a full ROM via TWRP without following our guide for rooted users.
- Download the full official ROM (Oxygen OS) and copy it to the root partition of your OnePlus 6T.
- Go to Settings > System > System Updates > tap the top right corner and choose “Local Upgrade”.
- Now choose the ROM zip file you transferred. It will install and then give you the option to reboot when it is finished.
If you install the full ROM through TWRP, your device will probably not boot afterwards. There are additional steps to perform.
- Download Magisk to your SD card, reboot to TWRP.
- After flashing the full ROM in TWRP, reboot back to TWRP.
- Flash the TWRP installer.
- Reboot your OnePlus 6T to TWRP, and flash Magisk.
Note: If you use the local upgrade route instead of TWRP, you can re-lock your bootloader, which enables widevine L1 for HD videos, and also gives you a certified Google Play device.
You can use the fastboot command fastboot oem lock, but be warned this will factory reset your device.