Lightroom crashes finally solved - Stupid me!

To speed up the Lightroom denoise feature I bought a Geforce RTX 3060 but Lightroom Classic kept crashing.

The reason: I did connect the DisplayPort cable to the motherboard with an onboard Intel GPU instead to the graphics adapter. 

After connnecting the monitor directly with graphics card, no more crashes! 

Anyway - it seems extremely unlikely that someone else made such a mistake!