Lack of storage space prevents startup

Hi all, my FP3 is shutting down immediately upon restart, because there is no storage space anymore. This makes it impossible for me to free up space.

I think my problem is very similar to this problem. That user decided to simply do a factory restart. I could do that, but I would lose all my Signal data (because I, yes stupidly, didn’t make a proper backup of that for some time).

I’m now reaching out to you, to check one last time if there is no other way out.

Some extra info:

I am running e/OS

The problem also happens when I start in safe mode.

I can get into the phone through adb shell (e/OS allows me to enable that from the recovery mode), but it does not give me any possibilities to remove packages (pm is not available in /system/bin) nor does it give me access to files (sdcard, storage and data are all empty folders).

(pm is not available in /system/bin)

Do you mean rm?
Is the command busybox available?