If you are not 100% pirating your content I would not suggest a linux setup.

I’m pretty sure they have jellyfin apps on Android tv. I have a cheap projector that is running, I believe, Android tv and I use jellyfin on it.

So the main problem with a Linux TV box these days is that you can’t get a decent experience with legit streaming services thanks to hardware DRM. So the best thing to do really is to have a Linux server (any mini PC will do), and to stream from that to the Android TV box via Jellyfin. I would recommend using Proxmox, as you can have Jellyfin, your downloaders, a nextcloud instance if you like, all in their own containers with a nice web UI to manage them.

For context: I personally use a 2015 Intel MacBook running Linux connected to my tv, and use a small wireless keyboard and trackball to control it from the couch. I’m actually planning on checking out KDE Connect after seeing it on https://hexbear.net/post/7662659

I’ve been researching some simpler options for my own parents since they use Roku which is somewhat limited and has ads. But a mini PC would be too complex for them. They need something with a simple remote and automatic updates. I think an Android box would make sense for their use case. I plan on installing something like SmartTube, PipePipe, or Tubular on it.

If your dad thinks he would like to do something like web browsing, email checking, or gaming on the tv, a mini PC is probably gonna do it better than Android TV.