• Ensure that the device is on the latest Android 10 firmware.
• Ensure that the device has at least 60% battery remaining.
• First: if you use anything else than a PIN code to unlock your phone, change it now. Last TWRP image for Android 10 asks for a data decryption password. It will be easier if it’s a PIN code. Go to Settings > System > Security and change your screen locking choice by a PIN code.
• Make sure your computer has adb and fastboot. Setup instructions can be found here.
• Make sure that bootloader is unlocked

The OnePlus 6T uses the newer AB partition scheme first introduced on the Pixel 1. As such there is no recovery partition. Instead, the recovery is part of the boot image. You will temporarily boot TWRP to perform and later perform a more permanent TWRP installation.

First: if you use anything else than a PIN code to unlock your phone, change it now. Last TWRP image for Android 10 asks for a data decryption password. It will be easier if it’s a PIN code. Go to Settings > System > Security and change your screen locking choice by a PIN code.

1. Prepare phone:
   1. Enable Developer options: Settings > System > About. Tap repeatedly on “build number”
   2. Go back to System, then go to developer options.
   3. Enable USB debugging
   4. Enable bootloader OEM unlocking, if present. Make sure that from now on, OEM unlocking option is enabled before you reboot. Sometimes, it might get disabled itself.
   5. Enable advanced reboot options.
2. Connect the device to your PC via USB.
3. Download all the files and put them on your PC:
   1. place Magisk & TWRP installer zip's
   2. place TWRP img on your PC
   3. place ROM image on your PC
4. Boot into fastboot bootloader mode. Open a terminal window, and type:

   adb reboot bootloader

   You can also achieve this via a key combination: With the device powered off, hold Volume Up + Volume Down + Power. You can also achieve this on the computer.

5. Temporarily boot into TWRP:

   fastboot boot twrp-img-name.img

   Wait for TWRP to start. Decrypt your data thanks to your PIN code. Swipe to allow system modifications.

6. On your computer, execute adb devices (it should list your device)
7. Transfer the TWRP installer to the phone, by executing:

   adb push twrp-installer.zip /storage/

8. In TWRP, go to Wipe, don’t check any of the advanced wipe options, and swipe to do a factory reset
9. Go to TWRP home, then install. Click on “Up a level” to go to your device drive root. Select “twrp-installer.zip” and swipe to execute.
10. Go to TWRP home, then “Reboot”. Select reboot to recovery.
11. You should now be in the durably installed TWRP. It won’t ask for your PIN code this time, and this will result to weird named folders in the “install” section if you go in it.
12. Go to Wipe and execute a factory reset
13. Transfer the ROM image to the phone, by executing:

    adb push stock-oos-9.zip /storage/

14. Transfer the TWRP installer to the phone, by executing:

    adb push twrp-installer.zip /storage/

15. Go to TWRP home, then install, click on “up a level”, go to “storage”, select “stock-oos-9.zip” and swipe to install
16. Go back to TWRP home, then install, click on “up a level”, select “twrp-installer.zip” and swipe to install
17. Go back to TWRP home, then go to reboot, and here comes the tricky part: note (and please don’t forget) the selected slot. Let’s say it’s A for this tutorial. If it’s B for you, just invert it at each step you see it from now.
18. Reboot to recovery.

1. PS: DO NOT BOOT IN OS JUST YET & CONTINUE TO THE ROOTING POST