C1083: Cannot open include file: 'vulkan/vulkan.h': No such file or directory

in file qvulkaninstance.h

So, can not build the app in 5.10

This happens if you include QtGui, or something that includes that automatically as this also includes qvulkaninstance.h which includes vulkan/vulkan.h. Unfortunately since this is not necessarily available it will cause a problem for any app that is using those headers.