How to reproduce:
1. Open 'SampleScene' from "CubemapNativeBugv2.zip"
2. Build and run
4. Press Enter/Return key
5. Inspect the changes to cube and skybox

Expected result: Skybox and cube become colored red, do not change otherwise
Actual result: All textures become black(Nvidia) or Skybox becomes red but has 1 face repeating(AMD)

Reproducible with: 2019.3.5f1, 2020.1.0b1, 2020.2.0a2
Could not test with: 2017.4.37f1, 2018.4.19f1 - Editor crashes

Reproducible with graphics APIs: Direct3D11, Direct3D12, Vulkan(Windows, Android)
Not reproducible with graphics APIs: OpenGLCore(Windows, Mac) OpenGLES3(Windows, Android, IOS), OpenGLES2(Windows, Android), Metal(IOS, Mac)

Notes:
1. Using Graphics.CopyTexture from created Cubemap returns all 6 faces correctly
2. Texture on the cube becomes black only on Vulkan (Nvidia, not tested with AMD)
3. Opening preview of the resulting Cubemap via Ctrl+Click produces the following 2 errors 6 times, even if source Cubemap has Read/Write enabled:
"Texture is not accessible."
"Can't read from cubemap"