I also ran into this problem on my FP4 (storage full) and had the same problems as @Ecowano:
I couldn’t mount even the encrypted data from recovery and neither could TWRP.
I did however manage to find a pretty wonky solution that allowed me to free space:
- Installed TWRP to recovery
- Booted TWRP
- Opened an adb shell
- Modified
/etc/fstabto mount/system_rootas writable (replacerowithrw) - Followed this guide to enable debugging (note that TWRP mounts the system partition to
/system_rootinstead) - Booted into the system without unlocking it and tried adb shell, you should see a message about this
- Unlocked the system and quickly checked allowing future access and accepted debugging access
- After the system rebooted by itself to the lock screen again, ran adb shell to gain a shell
- User data was still not mounted but I was able to use
pm uninstallto remove a large app (inspired by this comment)
This may work without installing TWRP but I already had that installed to my recovery partition.
IMHO the fact that filling up userdata can so easily brick the system is pretty bad and not in line with /e/OS’ aim to be an OS for everyone.