Open a terminal window for unRAID, navigate to where you are mounting /config. In that folder will be another "config" directory, delete or rename system.xml and migrations.xml and restart the container.
Jellyfin 10.10.7 (Docker)
Ubuntu 24.04.2 LTS w/HWE
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
4x WD Red Pro 6TB CMR in RAIDZ1