"Your data may be corrupt": /e/os booting into recovery and crashing on startup after running out of disk space

[AnotherElk]

@santa-klaus

I can also navigate back into a recovery menu. When I select try again, the phone starts up as normal. I get then to unlock my SIM. However, as soon as try to unlock the normal lock screen for the first time, the phone will crash.

@santa-klaus

I have gone through the recovery and fastboot menus, trying to find anything that could be of help. I was able to activate ADB and browse around in the file system using adb shell

So, you have ADB set up on the computer side, it seems.
If you connected to your phone before via ADB when /e/OS was booted, and if you granted this access to the computer then when prompted on the phone, and if you chose to remember this decision (the prompt includes this option) … then you should be able to access the phone via ADB before unlocking the SIM. And with this, you would get access to your data.

@santa-klaus

The recovery also gives me the option to install an update, e.g. via adb sideload. I have not tried that, since I don’t know how to do so and if it will give me access to my personal data.

There is no further update currently. In case you’re on plain 1.9, the available 1.9.1 would be the same for all we know.

For trying to install the same version you would still have to know whether you are running a dev or a stable build to be able to use the correct install file.
Furthermore, install files for use with ADB sideload aren’t publicly listed on the FP3 download pages, you would have to get the corresponding download links out of here (dev) or here (stable).