Valve seems to be testing ARM64 and Android support on Steam, as per a new SteamDB leak. Popular titles like Left 4 Dead 2 and Garry's Mod are being tested with "proton-arm64" tags, among others. This could hint towards new future Valve hardware running on ARM64 architecture.
My Steam Deck plays a lot of games, more than I even expected it to. Honestly I’m not sure where this “iffy library” crap comes from.