Dear fairphone community I am writing to you in what could be the last message from the living time of my beloved fairphone because in a few minutes I will attempt to relock my bootloader and it might very well result in it getting stuck in some other dimension.
I do this after having followed through the steps of forum members cosmic along the method given by forum member Hirnushi which I must precise was not easy and had specificity regarding DivestOS although eventually I managed to reset get_unlock_ability from 0 to 1 and put the OEM unlock toggle from OFF to ON
EDIT
I have commanded fastboot flashing lock_critical and fastboot flashing_lock and my phone sucesfully booted again into divestOS and also I have sucessfully rebooted two times.
However do not consider that it is possible to relock the FP4 bootloader out of the box after installing DivestOS because chances are that it will result in a Fair Brick.
The steps I followed require to extract a boot.img from the payload.bin file in divestOS zip file.
To do this I used https://forum.xda-developers.com/t/tutorial-android-ota-payload-dumper-on-android.4061799/
Then patch boot.img with Magisk following Hirnushi’s method described on posts 100 to 120 on the topic
https://forum.fairphone.com/t/trapped-in-fastboot-mode-with-locked-bootloader-and-corrupted-custom-rom/80985/117
Additional interesting reading
https://topjohnwu.github.io/Magisk/install.html
Check before attempting to lock that fastboot flashing get_unlock_ability = 1 and the toggle in developper option named OEM unlock must be on the position ON
After issuing flashing lock my device has rebooted 2 times and showed a message saying approximatively
“Your device has loaded a different operating system
Press power key to pause boot
Visit folllwing link with another device g.co/ABH”
Followed by 4-5 lines of Random numbers
And now I do not have the message about unlocked bootloader anymore; The message I showed previously appears at boot instead and I do not know what it means exactly and if it also shows on other OSs with locked bootloaders.
Also I do not know after having used magisk and messed around the system wether Android Verified Boot is implemented or not. Should someone know how to test it or enlighten me why it might or might not have been broken I might be interested.
SeedVault efficiently restored my app and files after relocking.
Forum members Hirnushi and Cosmic should be credited for inventing and pioneering the method presented here and SkewedZeppelin for an awesome OS and invaluable personalised support here and in the community of DivestOS