When runnning with Metal Editor Support turned on, artifacts will appear in the scene view if a gameobject is selected while the skybox and lighting are disabled.

Reproduction steps:
1. Create a new project
2. Add a cube to the scene
3. Turn off the skybox
2. In Scene View tab, toggle Scene Lighting setting
3. Inspect the scene

Expected result: No artifacts are rendered
Actual result: Many artifacts are rendered

Seems to occur across all supported versions of Unity, the OS version or hardware is the differing factor. Note that Enabled lighting or the skybox in scene view will fix the issue. Turning off Metal Editor Support also fixes the issue.

Reproduced using the following MacOS versions: 10.15.6