Nice to see people finally testing it : D
The thing is, normally Vulkan is very verbose and specific with its error messages. It surprises me a little that there is just a black screen, or random glitches. I don’t think the reason lies within the specific graphic context implementation, since its logical flow and structure is almost identical to the JUCE OpenGL context. But there is definitely something missing. I have a few guesses, like unsupported swap chain image formats. Driver specific stuff.
Unfortunately I don’t have the time/capacity to look further into this. Can’t replicate it here, so where to begin? My recommendation: Someone with the problem has to use a debug tool like RenderDoc https://renderdoc.org/, start the application, and look for errors. Or at least try to find the time/location in code, when it happens.