access to media

[TheDreadPirate]

Regarding having to setup Jellyfin again. When you configured Jellyfin, did you specify folders on the NAS to store /config and /cache? /config stores all your permanent Jellyfin data, including accounts. If you didn't, that data only exists on the ephemeral file system for the docker container and will be lost when upgrading or reconfiguring the container.

As for permissions, I'm not familiar with how UGreen handles that. You both need to ensure that Jellyfin has permissions to read it AND map that path on the host into the container. Otherwise the container is unaware that it exists.