Transparent objects not rendering with 'Physically Based Sky' in a Screen Space - Camera UI setup

Hello,

I hope this message finds you well. First of all, I’d like to apologize in advance if my English isn’t perfect and kindly ask for your understanding.

To use 3D objects in a UI, the CanvasRender Mode is set to Screen Space - Camera, and a new camera with its Culling Mask set to UI only is created and applied. This setup allows the use of opaque and transparent 3D objects within the UI. However, transparent objects placed in the world space do not appear. After investigation, it was found that changing the Sky Type in the Volume Profile’s Visual Environment from “Physically Based Sky” to another type makes the world-space transparent objects visible again.

Why is it that transparent objects in world space do not appear when using “Physically Based Sky” with the Screen Space - Camera render mode? Furthermore, is it possible to make world-space transparent objects visible while still using the “Physically Based Sky”?

For reference, I am using Unity version 6000.0.3f1 HDRP DX12.

Thank you very much for your time and assistance.