Update:
Since I have a Homebridge instance already setup for Ring stuff, I used the Homebridge plugin for Hubitat - authored by @tonesto7 - to re-map all of the devices that were configured in the built-in Hubitat HomeKit app. I then deleted the HomeKit app on both my C-7 and C-8 hubs.
Been using this for about 48 hours now, and no more "No Response" errors in the IOS and MacOS Home apps. This is the only change I've made to my overall home automation network.
Prior to the availability of the built-in HomeKit integration in Hubitat, I used the Homebridge plugin and experienced great stability, so I would expect the same now that I'm back to that setup. I'll run with this for a while, until we see some definitive explanation about why it suddenly became flaky after the recent firmware releases. The IOS Home app is the primary interface to the home automation for the family, and I was getting an earful from everyone the past couple of weeks. Problem solved for now.
This describes my network configuration and recent experiences with the Hubitat HomeKit integration exactly. Interesting that I only experience the "no response" condition on my C-8 hub, but not on devices mapped to HomeKit on my C-7 hub. Both hubs are always upgraded to the most recent Hubitat platform version (currently at 2.3.9.158) at the same time.
I am using Homebridge for other devices (e.g. Ring cameras and sensors), also node-red's 'node-red-contrib-homekit-bridged' to synthesize several HomeKit devices; all of these are performing flawlessly, with no interruptions. Only the C-8 mapped HomeKit devices fail.
