What filesystem are you using on the external drive? If it is NTFS or FAT, they won’t store permissions on the filesystem, which would explain why the owner/group changes are not persistent. To fix that, you can set the uid/gid on mount in your fstab.
What filesystem are you using on the external drive? If it is NTFS or FAT, they won’t store permissions on the filesystem, which would explain why the owner/group changes are not persistent. To fix that, you can set the uid/gid on mount in your fstab.
/dev/mapper/YOUR_DRIVE /path/to/mnt <fstype> rw,uid=<jellyfin_uid>,gid=<jellyfin_gid>,dmask=0002,fmask=0113