How to access TWRP to install LineageOS

[struppi]

When trying to install TWRP from fastboot, you have to boot directly into the newly flashed TWRP afterwards, like described here:

Cannot update TWRP

The solution is to press and hold the Volume Up button while rebooting directly after flashing the TWRP image. This will make the phone boot the upgraded TWRP. Afterwards you can safely reboot to system.

Hope this helps