My experience so far:
After downloading the game it managed to start the splash screen once. After that, pressing play would't even start the game.
Following a tip LeChat, who told me about this thread, I have downloaded the archive from YellowApple and extracted it where instructed. The directory compatibilitytools.d didn't exist, so I created it before extracting.
Even after selecting 'proton_5.0-local' in the combo, tThe game still wouldn't start.
After reading a bit more, I upgraded nvidia's drivers to 440 and renamed Bannerlord.exe.
Now the game starts but I'm stuck on the calibration screen. I don't even know where to look for any applicable logs.
I'd be grateful if someone could point me in some direction.
EDIT:
Disregard that post, after a 2nd attempt I passed the brightness calibration. I checked that I had 'proton_5.0-local' in the combo, I had, and still re-selected it anyways.
EDIT 2:
3rd launch, the mouseclick don't work
4th launch, they work again. weird.