Not op but also don’t have a steamdeck, but my tv setup is also reported as steamdeck. I use Chimera OS on my PC connected to my living room tv.
It uses just some old parts left over a 4 gen i5 and a Rx 470.
Everytime I hear something about Plex I become a bit happier with my choice for Emby as media server.
At the time of building my then server I could choice between them(jellyfin wasn’t a thing yet). Luckily I picked emby
Did you turn on steamplay/proton on in the settings? Including the toggle to use it for all titels?
Of course does not mean all games are playable, but they at least should so up in your library to try.
You can test a windows game and especially single player games most just work. If you have some problems you can check it on protondb.com. Maybe someone already found a simple solution.
Oh yeah good idea!