Kodi was designed for this. In the other hand, I’ve always found Kodi kind of mediocre for media management. I never got stuff like YouTube plugins to work reliably and the interface is kind of all over the place in my option, like a cable box from the early 2000s.

I’ve added Netflix and Jellyfin to my Steam Deck and they work surprisingly well with Steam’s controller interface. You should be able to replicate this with Steam Big Picture mode as well. If you have a gaming PC, this setup could also double as a Steam Link for gaming on the couch.

The basic setup was something like this: install Chrome or a Chrome fork of your choice, install whatever website you want to add as a PWA/offline application through the menu, then add that desktop item to Steam. Reload into gaming UI (or I guess big picture mode?) and you should be able use the controller to navigate a browser from there.

Depending on your controller of choice, you may also want to edit the controller’s key bindings in the Steam settings, i.e. make one of the buttons act as whatever key skips forward/back.

This setup only really works if you have some kind of existing UI you want to controlerify, like Netflix or Jellyfin. If you just have media files, this won’t work.

Alternatively, you may be able to set up Android TV on the mini PC through a distribution like lineageos. You get to decide if you want to go with the barebones default or if you want to add Google Play, but either way you should get a pretty usable TV interface out of that. With an HDMI CEC adapter you may even be able to use your existing TV remote to control it!