Edit2: OK Per feedback I am going to have a dedicated external NAS and a separate homeserver. The NAS will probably run TrueNAS. The homeserver will use an immutable os like fedora silverblue. I am doing a dedicated NAS because it can be good at doing one thing - serving files and making backups. Then my homeserver can be good at doing whatever I want it to do without accidentally torching my data.

I haven't found any good information on which distro to use for the NAS I am building. Sure, there are a few out there. But as far as I can tell, none are immutable and that seems to be the new thing for long term durability.

Edit: One requirement is it will run a media server with hardware transcoding. I'm not quite sure if I can containerize jellyfin and still easily hardware transcode without a more expensive processor that supports hyper-v.