I was actually just coming to say I figured it out myself, yep, mkdir overlay.
To be honest it's late, and was a bad idea for me to continue to mess with this tired. But since I never saw it asked, I figured worst I could do is look silly.
So I grabbed another Orbi LBR20, as I got one to work pretty well and was comfortable kicking around in ssh on my current runner.
Trying to set up V9.2.5.2.26SF I first reset to stock and then installed LBR20-V2.5.2.20, then installed V9.2.5.2.26SF, I couldn't see /mnt/circle/overlay so I then...