Ich bekomme die Meldung “internal server error” und scheitere an folgenden Punkten:
- Wo finde ich bei dem Snap die Logfiles? Jedenfalls nicht mehr unter …/data
- Folgendes sehe ich, wenn ich einen Bildschirm anschließe:
Wie gehe ich vor?
Your server appears to be having disk problems. This isn’t a snap or Nextcloud problem.
Did you system crash or lose power unexpectedly recently?
Ihr Server scheint Festplattenprobleme zu haben. Dies ist kein Kinderspiel oder Nextcloud-Problem.
Ist Ihr System in letzter Zeit unerwartet abgestürzt oder hat es einen Stromausfall gegeben?
It crashed, then I powered the computer off. It’s running headless.
Where can I get infos on how to repair the SSD?
Check your OS distribution’s documentation. 
In general, your system thinks it’s in a state where a manual filesystem check will probably be required (at a minimum). There may also be some further clues scrolling through the output of dmesg output. That’ll give you an idea of what went wrong during boot-up when your filesystems were mounted.
If I would be able toi copy the nextcloud snap folder, would it be possible to restore my Nextcloud setup by copying this snap to another machine / new SSD?
I created an image of the disk via mSATA-to-USB, bought a new SSD, wrote back the image and it worked. Now I will set up a backup script
The more often I started the computer with the defect SSD, the more files got lost and in the end the computer even did not start with the defect SSD. So it is true: The earlier you take a snapshot from a defect drive, the better.