When launching a Steam game on ONMO+, Steam will open in the background of your virtual session to handle login and game startup.

Do not close the Steam window during this process. If Steam is closed while logging in or while the game is loading, there is no way to reopen it within the same session — you will need to quit and restart the session to try again.

Simply wait for Steam to complete the login and for the game to fully launch before interacting with any other windows.