I managed to solve this with Android Debug Bridge (USB debugging was already enabled, luckily). Imanaged to uninstall an app that way, freeing enough space so the system resumed working.
For reference: In my case, the following steps helped:
- Download ADB from here: https://developer.android.com/tools/adb
- Unpack the zip file to the Desktop (anywhere works, this is just for the example)
- Open Terminal (on Mac. I am sure the process will work similar under other OSes)
- Enter
cd /Users/user/Desktop/platform-tools/(exchange “user” with your username) - Enter
./adb shell pm list packages. You will get a probably surprising long list of packages. Look for an app you know takes up a lot of disk space. Maps apps are a good bet – due to the map data, they usually need a lot of space, and can easily be re-setup if needed. - Enter
./adb shell pm uninstall --user 0 net.osmand.plus(replace “net.osmand.plus” with the app you want to uninstall (the rest of the line afterpackage:). - Try to reboot. For me it worked after the first try, you might need to uninstall additional apps.
Once you have regained access to the system, it might be prudent to head to Settings → Storage and free some more space.