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.
I have debian stable with xfce on a 2014 laptop. Increasing the fonts size and using KDE connect for remote on the phone to control the whole thing. Works smoothly for video and internet, just what I need.
It's tedious when you need to run terminal commands so I have an SSH server running there too.
For gaming maybe you want to consider moonlight utility, to stream steam games from your gaming PC to your TV PC. It's decent for most games but forget competitive shooters.
I can do 2 out of 3. instead of running the abomination that is Kodi, you can install normal linux to the Pi (Raspbian), and then add on jellyfin-mpv-shim (or plex-mpv-shim) and macast (for youtube, peertube, etc and it also supports DLNA). they are sinks, i.e. there is no UI for you to interact with. instead, you use your mobile phone or tablet to browse your library, youtube, whathaveyou. when you want something played, you send it to the sink and it plays it in full screen. you can use the mobile device to control playback (pause, ff/rew, change subs, etc.).
can't help with the gaming part, moonlight/sunshine should do that but I haven't got any experience with them.
the Pi 4 you got is more than adequate for all the mentioned tasks.
I currently have a Pi running OSMC (basically Armbian - Kodi) which I am going to replace with my old desktop gaming PC, a Ryzen 3600/GTX-1080 rig, which can run Steam and any game I want to play on the couch with a controller locally under its own power.
I understood you fine. what I'm saying is, you don't need to use the 1 KW PC when the 5 W Raspy can fulfill all the roles you stated - media playback (local and online) and remote gaming from your new rig. if you know Raspy's power by way of the crap that is Kodi - a bloated, slow as molasses, buggy zombie patched for 20 years and held together by duct tape - then you might be surprised with how it can run. also, you have the option of running LineageOS AndroidTV with native apps for all three stated roles.
if you're adamant about repurposing your old PC it in that role, your best bet would be bazzite, a 10-foot UI-having SteamOS clone. but then, you're smashing into the wall that is Nvidia on Linux; a fun project but not really a plug and play solution for the living room.
I used to run Steam BPM under steamcompmgr, and had Kodi as a shortcut via "add a non steam game". You could do a browser similiar way. steamcomomgr is a X window manager that handles scaling for those small dialogs for TV screen. Gamescope is similiar for Wayland.
Now I have Debian stable running plasma-bigpicture, which is a KDE set up for TV screen. Flatpak gives the latest Kodi and other apps that the OS doesn't keep up to latest version, and I do enjoy the stability of the underlaying OS for HTPC use.
Which is better? It depends. If you do mostly games and Kodi, and use a game controller for controll, then Steam BPM. It has a controller friendly OSD keyboard for text, and the upscaling of starting dialogs especially for older games if a nice feature. For youtube, this may not be the best option, and it needs a bit more work to set this up for the Display manager as a xsession.
Plasma-bigpicture is nice if you want to run apps made for traditional desktop, and have a keyboard and mouse. Say for youtube you may want to use some unofficial players to get rid of ads. You can set Steam to auto-start on the background to get game controller input working on the desktop. Setting this up is as easy as installing one package, and switching the session via login manager.
Ofcourse, you can have both and switch from you login screen. You can't have Steam running on the login screen for that game controller friendly keyboard for login, but you can set automatic login for the one you use most, and switch by logging out.
As for distro, pick the one you like most and know your way around.
I have a hardkernel station m1 running android TV. You can set up with or without the play store, I did mine with. It's great. The main control is a remote from the couch.
It uses flauncher for the 10' UI and runs tivimate for iptv. I added a cheap nvme drive for dvr functionality. Other apps include stremio, YouTube, steam link, retroarch, vlc, etc.
I've tried out Steam Link on my Pi 4 in OSMC. It's bad. Couldn't pipe sound from my desktop PC to the Pi, so I'd have to either use my bluetooth headset on my desktop...being unaware of that software's existence improves the lives of millions of Americans every day.
Try again with the recent version, they updated it for current Debian Bookworm and added Pi 5 support. If audio doesn't work, you might have problems with the Steam streaming speaker driver on the host machine.
I didn't like big picture mode from the TV much, especially for media. I stuck with just using a lighter DE (Mate in my case) with some tweaks to make it easier to read from the couch and use a wireless smaller keyboard and trackball.