Hello, I just want to report that I had the same or very similar problem with e.OS on Fairphone 3 today. I use Signal with automatic nightly backup. The low disk space warning started showing just a few days ago and I did not take it very seriously. I noticed that the Signal backup failed yesterday, but the phone kept working. I was planning to do a clean up soon. Today, the phone crashed a few seconds after the Signal backup started, and it booted into recovery. When I tried I normal boot, I could enter SIM pin and e.OS pin, but just after entering e.OS pin the phone shutted down and rebooted like described by others.
Thanks to your tips, I was able to recover:
- Press back button in Recovery and enable adb
 - Download Android SDK Platform Tools ZIP-file to my Windows PC, extract and
 - run adb shell
 - In the shell, mount the encrypted userdata and search for big files:
 
mkdir -p /mnt/userdata
mount /dev/block/bootdevice/by-name/userdata /mnt/userdata/
cd /mnt/userdata
find . -type f -size +1000M
- I found three 4GB files. From the time stamp and size I guessed it must be the Signal backup files
 
cd /mnt/userdata/media/0/6mYlOAlMZSpGmEFPQ+NQSB/
FP3:/mnt/userdata/media/0/6mYlOAlMZSpGmEFPQ+NQSB # ls -l
#total 11819828
-rw-rw-r-- 1 media_rw media_rw 4112204390 2024-05-08 01:11 _+PUxYaUpHxYqeDg7GQFEJPqOtSVPZE5c
-rw-rw-r-- 1 media_rw media_rw 4119633920 2024-05-11 23:44 _6dlwmfhlImbpUs6i69EBi7zx3wl10ptb
-rw-rw-r-- 1 media_rw media_rw 4113810646 2024-05-09 00:58 _op3ODN,RCuUsWstppIIfJbKLfh6jo8J,
- Now delete a file and hope it is really just a redundant backup and nothing very valuable
 
rm _6dlwmfhlImbpUs6i69EBi7zx3wl10ptb
- Unmount
 
cd /
umount /mnt/userdata
exit
- Reboot phone. Now it does not crash anymore.
 
Whew, I think this is a bit too exciting for a ordinary case of device storage running full. I guess there should be some more protection against this…