Dude, with the exception of Gamepass, Linux gaming is really easy.
If you’re okay with Redhat/Fedora, using Nobara Linux (it’s a spin-off, unofficial, but by the guy who does a lot of the Proton [magic compatibility sauce] stuff, GloriousEggroll, who AFAIK is a dev at RedHat) literally installs everything you need.
Steam → Steam
GoG/Epic → Heroic Launcher
Amazon/Blizzard → Lutris
Gamepass → You have to use the cloud version with Edge browser
Click, install, game.
There’s only a few Anticheat PITA titles still (I believe Valorant is one) that won’t work.
Jellyfin happily runs on a pi, but really only for direct streaming.
You’re generally better off just making the pi a samba server and connecting to it in Kodi. For jellyfin, you really do want a 7th Gen Intel or better (old 7100t-based thin clients are «chef’s kiss»).