True, I have a wired Apple TV which I try to ensure is always my primary HomeHub but it does seem to just change on a whim from time to time - there's about 15 candidate hubs in the house!

> Apple TV which I try to ensure is always my primary HomeHub

How?

I was under the impression that you cannot actively decide which device becomes the primary one?

I 'only' got a wired ATV and a HomePod mini - and the mini is the primary hub way more often that i'd like it to be (like... none of the time, at all :) )

It's a royal pain in the arse, but it involves unplugging every candidate hub and plugging them back in again in the preferred order. Can't say for sure, but I think the points where my preferred order has changed without me doing anything were down to very short power cuts during the night, when that happens, you get whichever device boots back up first as your primary hub.