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.
But seeing as we recommend ditching the launcher with the '--skip-launcher' launch option in the game's properties within Steam, that hasn't really been a big issue for us anyways.
There were also instances in the game where, when you were required to enter text, it wouldn't necessarily automatically bring up the Deck's keyboard and you'd have to invoke it yourself.
But no more. Baldur's Gate 3 is now full compliant, and is only set to get more compliant when Larian gets around to adding FidelityFX Super Resolution 2.2 support to the game closer to the PS5 launch in early September.
At the moment it only supports the first generation of FSR, which has nowhere near the (excuse the pun) visual fidelity of FSR 2.2.