You should check out jellyfin-mpv-shim, it basically hooks up mpv to Jellyfin's cast system, so you can control mpv from other Jellyfin apps. I have a setup sim

You should check out jellyfin-mpv-shim, it basically hooks up mpv to Jellyfin's cast system, so you can control mpv from other Jellyfin apps. I have a setup similar to your NUC and it works really well.