Baldur's Gate 3 is now rated as fully "Verified" for Steam Deck, which is a change from launch where it was still rated with certain caveats. That means the game is completely functional with the default controller and graphics settings.
To be honest, you could already play Baldur's Gate 3 on Steam Deck before this, the only slight issues were that when it wasn't connected to a network for some reason that made it want to use the Larian Launcher. And that meant you needed to mess around with the touchscreen and potentially keyboard input if you actually wanted to log in.
