I have an old AMD FirePro D300 2 GB on a Mac.
I'm using Godot 3.2 stable. GLES3.
Yes, I have fog and procedural sky on in WorldEnvironment (no dof or ssao).
No issues in perspective view, only orthogonal.
I'd share the project but it's in such shambles with dozens of subversions each testing something else, it'd be embarrassing.
That being said, I am on a Mac, so I should try rebooting as there may be a process running in the bg impacting performance (this happened before, although I'm not sure why it would impact only orthogonal and not perspective...).