When creating a new HDRP template project the example scene opens black. It seems the reflection probes in the hierarchy are the cause. Disabling the probes fixes the scene.

How we can reproduce it using the example you attached
- Open Unity 2018.2.0f2 (Release Version) with a MacPro
- Create a new project with the HD Render pipe template
- Wait for scene to load
NOTICE ISSUE >> Scene renders. After a few seconds it goes black.

- In the Hierarchy, disable reflection probes under "Example Assets"
- Scene renders.

IMAGES ATTACHED

Tested on two MacPro Radeon Pro 560 4096 MB, Version 10.13.5