Have been running into a bug with Proton 8 and higher recently. Apparently it's a known issue. Proton 8 + certain pre-requisites + Nvidia drivers result in a no launch due to pre-requisites not being installed/updated.
The workaround is to switch to Proton 7.0-6 and let the pre-req install. Then after the game fails to launch, stop it, and switch back to 8 or experimental. Also for unknown reasons, if you have mangohud installed (even if you're not using it), you have to add mangohud=1 in the launch commands. If not, it simply will not launch.
I'd hoped Valve would have addressed this by now, but it's been going on since Baldurs Gate 3 officially released about a month ago.
This does not appear to impact AMD users, but I cannot confirm as I only have Nvidia cards.
