I put together a Steam Configuration on the Switch Pro Controller for RotMG; you can play Realm with a controller on Steam! [includes details and general Steam Controller How-to Guide] : r/RotMG
CONTROLLER CONFIG FOR STEAM - PLEASE READ! - BloodbornePSX community - itch.io
Getting Started for Players (Steamworks Documentation)
Valve starts roll-out of the Steam Deck controller configurator to desktop Steam | GamingOnLinux
How To Setup Any Controller On Steam - Xbox, PS5 Dualsense, and More - YouTube