Look up naskiller builds. Gives you lists of compatible, cheaply sourced hardware for a good nas. I built one a while back and i’ve been really happy with it. Cost about 600 bucks, and it rivaled my new couple thousand dollar laptop at the time. Only thing I wish i’d done differently is not prioritized small footprint so much, because i’d really like to have more slots for video cards, etc now that llms are a thing.

Also, consider whether you’re comfortable fixing unraid or truenas, because Debian with mergerfs and snapraid is perfectly fine for mostly media, and it’s way easier to fix if something goes wrong.