Does not reproduce: 2021.1 + Master
Reproduces on: 2020.2.0b10/b11 + 10.2/Master

Reproduces only on 2020.2 binaries!

Steps to reproduce:

1) Open attached project or start a new HDRP one
2) switch to Vulkan
3) Go to Window -> Render Pipelines -> Debug
4) Try any full screen debug modes in Material section. Observe everything renders as black now
5) Try MatCap toggle from sceneview (!!) button, observe it doesn't work as well.

Note: Reproduces also on Metal!
Interestingly Lighting -> Debug Mode -> MatcapView works fine, although with horrible performance.