I never thought of it until I saw fuscia’s thread on the issue, but now that I have it in my head, I can’t seem to get an answer. I don’t think anyone does OB as the default desktop.
Even fuscia could only come up with Grafpup, a Puppy Linux-based distro aimed at graphics packages. Apparently it now uses IceWM and will be going to Openbox in the future.
If it does, I might choke back my dislike for Puppy and give it a shot.