I used an Apple TV 3 as a HomeKit Hub for years.
Apple broke the functionality with iOS 13, without saying anything or claiming that Apple TV 3 was still compatible, but it didn't work, except once in 20 attempts.
Then I used a used gifted iPad mini 2 for a year, always plugged in and off every 24 hours.
Apple has never given any support on that feature.
A terrible year, nothing worked in the house anymore.
I bought HomePod mini in Germany because it was not available in my country, booked before it was bookable on the official website, received at D1, I think the first active in my country, so much so that even in the Apple Store they were amazed when they saw it in my account and asked me how it worked, if it was okay, while not supporting the language.
It went pretty well, not like Apple TV 3, but occasionally it loses connection or sync with accessories, all strictly HomeKit (not Zigbee or other protocols). iOS 14/15 is to fault.
I would also like to buy a second HomePod mini for the stereo but I'm waiting for the one with the screen in advance some time ago.
Meanwhile, the Apple TV 3 and the two Airport Express 1 and 2 work great.
Apple has lost a lot of quality over time, although those who haven’t been a user in decades don’t understand it.