I can recommend the dietpi OS; it is a minimal os that comes with a package manager for installing containers for things like radarr, sonarr, deluge, and jellyfin, which will allow you to download/watch movies(find on radarr, download with deluge, watch on jellyfin) and tv shows (find on sonarr, download with deluge, watch on jelyfin) in a fairly autonomous way. Its a bit of setup if you havent done it before it might not be for you but once its running its fairly seamless.
I’m using nvidia right now with a 3060. It doesnt use much power, I got it for pretty cheap on ebay, and it encodes/decodes everything except for av1 encoding which I dont have use for. Looking at the charts in the link below, if you need to encode av1 you’ld need a 4000 series.
https://developer.nvidia.com/video-encode-and-decode-gpu-support-matrix-new
I’ve found nvidia to work pretty well for jellyfin, I use docker with the nvidia container toolkit and it just worked with hardware encoding out of the gate. I also have some other docker containers running gen ai and the 3060 handles them well as long as the modle will fit in vram.