It causes a bunch of weird controller errors, such as when a controller disconnects (or if the deck goes to sleep), it can't reconnect again.
Just let it use the default version (which I believe should be Proton Hotfix, or whatever Valve decides it should be since BG3 is an AAA headliner, they'll want this to work)
That's disappointing. Haven't tested it on the deck yet as I'm waiting for new screen to arrive. It runs great on my moderate gaming PC with a 6600xt. Runs at 1080p ultra and hovers between 100 and 120fps. Usually closer to 120.