Your username would fall under GDPR as personally identifiable information - also if your instance asks for an email address, that is also personally identifiable information under GDPR.
I think any posts that users can contribute to a social network, also fall under GDPR.
This is a potential issue that many instance owners may not have realised.
Your example didn’t really make any sense, as you can use Apple One on iOS 14 or newer. So the oldest supported iPhone would be the 6s from 2015, which at the point iOS 14 came out was already 5 years old.
I’m not an iPhone user, but they have better long-term updates than the vast majority of other vendors. Five years of support, I don’t disagree with them wanting to push their newest device - they are a business and want to make money. Most features work except for things where there are hardware limitations.
Since they are ZigBee, replace the Hue Hub with an agnostic ZigBee one.
Since you already use home assistant I would recommend this one - https://www.home-assistant.io/skyconnect/
https://zigbee.blakadder.com/zha.html - this is lis of supported devices, if you go for the default ZHA setup.
There are so many good ones out there there’s no reason not to use one.