I decided to try and upgrade back to 5.0.9766, and change the shader compilation. That solved the grey screen issue. However in both builds, the Vulkan backend took down my iMac with lots of graphical glitches when playing Super Mario Galaxy 2 (consistently and always at the same place). I had to power down the computer to get it back to life. So for now I will stick to OpenGL. At 1080p it plays at 100% of the games' fps, which is all good enough for me.
If anyone wants to know what goes wrong (with either the grey screen or the crash), I am happy to provide logs. Just point at what you would like to have.
If anyone wants to know what goes wrong (with either the grey screen or the crash), I am happy to provide logs. Just point at what you would like to have.