After moving Jellyfin to a docker container with different paths, I ran these SQL queries on the jellyfin.db in order to make images appear again.
UPDATE ImageInfos SET Path = REPLACE(Path, '/etc/jellyfin/users/', '/config/users/') WHERE Path GLOB '/etc/jellyfin/users/*'; UPDATE BaseItemImageInfos SET Path = REPLACE(Path, '/var/lib/jellyfin/', '/data/') WHERE Path GLOB '/var/lib/jellyfin/*'; UPDATE BaseItems SET Path = REPLACE(Path, '/var/lib/jellyfin/', '/data/') WHERE Path GLOB '/var/lib/jellyfin/*'; UPDATE BaseItems SET DATA = REPLACE(DATA, '/var/lib/jellyfin/', '/data/') WHERE DATA GLOB '*/var/lib/jellyfin/*';