SOLVED: Setting uid & gid of my user with official docker image breaks Jellyfin

[TheDreadPirate]

Did you remember to add the "group_add" variable and pass in the render group ID?

My docker compose for reference.

Code:

jellyfin-testing:
    image: jellyfin/jellyfin:10.9.7
    container_name: jellyfin-testing
    user: 105:104
    group_add:
      - "993" # Intel render group
    networks:
      blackmoon:
        ipv4_address: 172.16.100.2
    expose:
      - 8096
    volumes:
      - ./jellyfin-stable-data/config:/config
      - ./jellyfin-stable-data/cache:/cache
      - /media/library:/media/library:ro
      - /media/storage2:/media/storage2:ro
    devices:
      - /dev/dri/renderD128:/dev/dri/renderD128
    restart: 'unless-stopped'

I also have Jellyfin installed directly on Ubuntu and I piggy back on the UID/GID it generates for all my jellyfin test containers. But the important part is "group_add" for your problem.