Hi,
I think I’ve managed to identify the problem and the solution. The update to version 10.11.0 is a significant one and requires, among other things, updating the Jellyfin database. When you run sudo journalctl -u jellyfin.service -e, you’ll see an error message about insufficient space in /var/log/jellyfin. The space that DietPi assigns by default to the tmpfs for /var/log is 50 MB, but this new version of Jellyfin needs at least 512 MB.
What I did, and what worked for me, was increase the size of /var/log to 512 MB, which allowed Jellyfin to start without any issues. It completed the entire update process and is now running perfectly. Once the update was finished, I tried restoring the /var/log partition to the original 50 MB to see if the issue was only related to the update, but it wasn’t. If there isn’t at least 512 MB on that partition, Jellyfin won’t start.
TL;DR:
sudo nano /etc/fstab ←- change tmpfs /var/log tmpfs size=50Mb to size=512Mb+
sudo systemctl daemon-reload
sudo mount -o remount /var/log
sudo systemctl restart jellyfin
Cheers!