The problems with the HomeKit architecture upgrade might finally be fixed with iOS 16.4. At least Apple is planning a new attempt with the release of the software version. Corresponding hints have now appeared in the code.
The HomeKit architecture upgrade is said to provide improved stability and faster device response times. With iOS 16.2 released for all users, Apple had however withdrawn the optional upgrade about a week later.
In the beta of iOS 16.3, Apple started a new attempt, but decided against releasing the upgrade again in the final release. Now it is finally supposed to happen with iOS 16.4. This is proven by code snippets that have now surfaced.
However, it will probably take a few more weeks before Apple releases the new software version for all users. So far, not even the first beta has been released. However, this could change this week or next week.