I believe your issue is part of a much larger issue. Since Steve Job passed, Apple now seems focused on closed systems and generally no longer plays well with others with all their products, both hardware and software.
Given their current corporate behavior, unless you are already heavily invested in HomeKit, I would invite you to consider abandoning it completely and focus on other technologies such as Z-Wave and Zigbee. They all seem to work reasonably well with Alexa, Echo devices, and HE for voice control and do not share the same high price points as Apple.
While it may be a bitter pill to swallow, it might save you time, money and frustration in the long run.
Actually, Steve started that entire mentality at Apple. He wanted to sue anyone who came out with software products for the Apple II for trademark infringement.
Well it's opening up more as the base of Homekit is Thread which is an open source protocol (and free) and Thread+zigbee is a defined part of matter which apple has agreed on... Now that isn't to say Apple along with every other major company won't hobble their own implementation of matter but we shall see. (That is if matter even gets out of the gate). Now there is also no problem with mixing stuff, even apple. Of course it would be better if apple was not a walled garden, but oh well. Others took up the slack and were able to bridge stuff (Hubitat>Homebridge or Hoobs>Homekit) and they will continue doing that. Then of course there are more professional systems like Control 4 and what not that will strike financial deals with Apple and other closed systems in order to achieve interoperability. I have been in the industry for since 1978. Walled gardens aren't new. Jobs certainly did introduce the walled garden concept to apple. Jobs was not the first to do so in the industry, but he was the most noisy. IBM tried to keep a walled garden by suing clone makers for copyright. They even attempted to charge fees for writing for the XT. Hell even Atari tried to sue the makers of the ATR-8000 interface because they didn't like the idea of people being able to run CP/M on the Atari 800/400 because it also allowed the use of generic TEAC 5-1/4" drives and other generic components instead of the proprietary drives and modems that Atari had at the time. The bottom line is, things will evolve. Protocols will come and go. Nothing wrong with mixing things if they work for you. Tomorrow z-wave could be gone if matter takes off like a bullet (or it could continue and evolve into being integrated into matter, who know). Keeping all your eggs in one basket so to speak is certainly not a long time goal that should be striven for. X10 people will tell you that.
