I recently added a used mini pc to my lab and it has a Ryzen 3550H, 16GB ram and 512GB nvme; it cost less than 100€ total, hits almost 8000 passmark. Just to give you an idea of what you can get on the used market, I wouldn’t buy a new Celeron pc myself.

A lazy option to set up a player (what I do a t least), is installing via flatpak Jellyfin Media Player. For android, installing from F-droid.