Wow! Thanks for sharing these tips. I’m sure these will help other people. As I mentioned, I’m not that experienced with Unity and didn’t know about the unlit versus lit material.
Additionally, I encountered a peculiar situation where I had to choose “Universal Render Pipeline/Unlit” rather than the standard Unlit option to render the inside of the sphere correctly, despite flipping the normals.
Are you using the skybox as suggested by RicoB?
We were originally using a sphere with flip normals. However, most people started using the skybox technique to avoid the vertices.
The picture in your example looks fantastic.