Thank you all for your support. Yes, it was my attitude to Vulcan that gave me the crashes.
With OpenGL, the scenery extension works perfectly in 2D and 4K, also looks good, but ....
Who flies with this Innsbruck scenery in VR and perhaps still with z19/20 texture, should in my mind go to the Vulcan setting, because here the performance -"exploitation" is much bigger than that with OpenGL. With Vulcan, the Nvidia Manager can set everything you want to "Max" that the graphics card gives. The setting of HDR does not have to be dispensed with here either!
That's why I've now given up this really good scenery extension with a heavy heart, because I prefer to keep my previous, very vividly depicted VR scenery.