iOS 16.4 has broken HomeKit connections again

Here's what finally worked for me, after much online research and trial and error.

Using HomePod mini would not work as a reliable hub, even after plugging it into the MacBook and restoring it to factory which automatically upgraded it to 16.4.1. So left HomePod mini unplugged from wall.

Also confirmed both Apple TV's were updated to 16.4, and unplugged from wall. Then manually reset Logitech Circle View camera to factory settings, and unplugged from wall. Unplugged Ecobee 5 thermostat from wall (which manually resets it to factory).

Deleted Home app, restarted modem and router (set modem to 2.4 instead of dual band with 5), reinstalled Home App. Did NOT reuse default name of My Home, set to new name right from the start (suspect there is a "hidden" profile somewhere for the Home names which can't be accessed and is causing mixed signals).

Plugged in one Apple TV and enabled it in Home app which made it the hub (only appliance plugged in). Intentionally did not use HomePod mini as hub, and made sure the HomePod mini was last appliance added to Home app.

After that added in the second Apple TV without complication, then the camera, and eventually the thermostat, and lo and behold everything worked properly since the release of 16.2. Last, added in HomePod Mini which worked as well (at least for the last 3 days).

My anecdotal take is that HomePod mini does not work well as hub for whatever reason. Also feel not using the default My Home profile (which I had used in the past) seemed to help, but who really knows.

What a time consuming misadventure. Here's hoping someday Apple will get serious with HomeKit. So far it's been a huge disappointment to me, and makes me regret leaving the Google/Nest ecosphere which was much more reliable.