Comment by mort96
If it's going to be primarily a gaming device then that makes sense, but if not, what do you gain from SteamOS? And why do you want Steam to start on boot?
I use Fedora for this purpose, used to use Debian. You really just need a system with a web browser, file browser, media player and torrent client, and some way to remote control the computer from the couch (ideally from a phone).
Sadly, I don't know of any nice off the shelf solution for that last part. KDE Connect is an option but it kinda sucks. I've always had my own Remote Desktop web interface service type thing running on the machine (though Wayland has kinda thrown a wrench into that for now...)
> some way to remote control the computer from the couch (ideally from a phone)
If you use Kodi then you could try Kore (their remote app). I tried it once a long time ago and it was alright, but it's hard to beat a keyboard. I think similar apps exist for VLC and other media players, but I haven't looked into a solution that allows controlling the entire computer via a phone.