GamingOnLinux

Windows apps and games added to Steam on SteamOS / Linux now use Proton by default

Valve updated the Steam Client Beta with a useful change to external Windows apps / games getting added to Steam on SteamOS / ...
XDA Developers on MSN

Steam's latest beta update makes running Windows games and apps on Linux a lot easier

Add it to Steam and you're good to go.
BetaNews

Steam beta now runs non-Steam Windows games on Linux through Proton

Valve's Oct. 7 Steam client beta runs Windows programs added as non-Steam games on Linux through Proton by default and fixes two Browse and Stop button bugs.
VideoCardz.com

Steam now automatically runs non-Steam Windows games through Proton on Linux

Valve is simplifying Windows game compatibility on Steam Deck and Linux PCs. The latest beta removes the need to manually ...