After patch one my game crashing during the next fight that I have to do... 3 times already, there is no way around it, it seems

Try changing from Vulcan to DirectX or viceversa, good luck.

"the next fight" = means your game is booting and playing?

once you have 1 crash = the ui resets to bullshit ultra and you have to move everything back to something less silly

I also had problems with random crashes after Patch 1 installation (via offline-installers). They seem to occur tipically when I fast travel from camp to other map locations or, sometimes, when I load a game. Oddly, before patch 1 I had never exeperienced crashes, never at all!

Doesn't crash for me but even prior to Pach #1 I finally came around and updated to the latest GeForce drivers.
As I said not necessarily because BG3 was running like shite but maybe installing the latest GeForce drivers or your graphics card's equivalent solves any crashing you're currently experiencing.