Really, truly, reset Apple Home configuration

I started using Apple HomeKit in 2018, with an Apple TV 4K designated as the primary hub.

I added a Philips Hue light controller, multiple Eve temperature and air quality sensors, a couple of GE air conditioners. Automations worked fine, we were satisfied.

We added a second home to the configuration in 2019, with just a couple of lights.

All worked fine.

Until last fall when we found any attempt to use the Home app on our devices just stalled with the dreaded "Loading Accessories and Scenes" message.

As directed in various forums we reset our home configuration.

No joy, still the same error.

We logged out of iCloud on all of the devices in both homes.

We logged in, hit reset home configuration, and logged out again.

This time we were able to set up Apple Home again. From scratch, since there's no backup and no way to restore a configuration.

Except, when we went to add devices…they sometimes were still there, in the allegedly virgin Apple Home configuration. Reset does not mean reset?

This second setup lasted less than eight weeks before the dreaded "Loading Accessories and Scenes" messages appeared again.

Now I'm in a situation where after resetting Apple Home, logging out of iCloud, logging back in, some devices cannot be added at all, because Apple Home insists they're already in a home configuration, except not this home. Other devices get added to "Default Room" and remain there even after attempting to move to the correct room.

This is really disappointing. Is there truly no way to go back to zero with Apple HomeKit? Or no way to back up and restore a configuration? It feels like HomeKit is not really supported as a separate product or service, it isn't even listed as a topic in this community support and there is no apparent way to open an official Apple support query on HomeKit.

I was hoping to get away from Google Nest for home automation, but it's never been this nightmarish as Apple HomeKit is turning into for me.