@s710 said in How to revert to Android?:
Okay nevermind. Although the bootloader was already stating "DEVICE STATE - unlocked", and every reboot remindst of the bootloader being unlocked, I had to do fastboot flashing unlock_critical (which would ask again if I wanted to unlock the bootloader), and then the flashing tool for FF4 would run fine.
Android was successfully reinstalled.
Thanks for sharing! This post saved me quite some work.