I have an older model appletv that frequently tries to act as my home hub over my very new homepod. When this happens, all of my smart accessories that use matter/thread connectivity stop functioning. I am forced to unplug the appletv to let the homepod resume hub duties. Even better would be the automatic prioritization of hubs with the newest/best hardware.
You did not specify the model of your "older" Apple TV but it must be the Apple TV 4K (1st generation) or earlier. Only the Apple TV 4K 2nd generation, and the 3rd generation support thread.
However, the I think I am correct in saying that the Apple TV 4K 1st generation is capable of being a home hub and if so therein lies your problem if your thread devices are being silenced when this older device becomes the home hub.
Apple's support document Set up your HomePod, HomePod mini, Apple TV, or iPad as a home hub says
Thread-enabled Matter accessories require a Thread-enabled home hub, such as HomePod mini or Apple TV 4K (3rd generation) Wi-Fi + Ethernet, or a supported third-party border router.
The implication is that you need to update your old Apple TV with an Apple TV 4K 2nd generation or 3rd generation if your thread devices are to function properly. This is also the message given in If you see a 'Thread Border Router Required' alert on your iPhone or iPad:
Set up a supported third-party Thread border router or set up one of these devices as a home hub:
Other Apple TV and HomePod devices are not compatible with Thread network.
To address your message line - rather than the question under it - the device designated as a home hub will change if you have more than one. This is an automatic function determined by the Home software and not one the user can control.
Yes- I was already very aware of everything you stated in your reply. I'm saying that software controlling which potential hub is currently active needs to be updated to prioritize hubs with newer hardware capabilities, e.g. matter/thread. It currently seems to default to whichever hub is powered on first regardless of their hardware.
We need the ability to designate/prioritize home hubs.
