Distro/software for living room/TV PC?

So for the past little while I've had a Pi 4 hooked up to my TV as a Kodi box running OSMC, which has been okay I guess. Having recently built a new PC, my old Ryzen 3600/GTX-1080 box is freed up, so I'm thinking of replacing that Pi with something that can also run Steam.

I'm completely at a loss for what system to run for a living room couch/TV experience. Kodi...could be better, OSMC doesn't have a desktop and won't launch just a normal web browser, it uses Kodi as its only UI and it's just not fully good enough.

I'm also not sure if Steam Big Picture Mode is capable of being a media center. Like, can it play movies from there? My experience with Steam's Big Picture Mode is it runs like microwaved shit anyway, feels as responsive as the average dogwood.

I want to be able to get to my collection of movies on my NAS, play Steam games, and do some web browser tasks like watch Youtube and that kind of thing. I just don't do the streaming services, I don't need Huflix or NetMax or whatever.