I tried to use a Homebridge plugin to control my SimpliSafe but it was for version 3 and I have version two so that’s when I went with my hardware hack. Did waste some hours trying to get it to work.
As far as the rachio the plugin would allow control of the zones but would not fix the issue of not being able to query the controller when it disconnects from homekit.
Honestly I’m pretty close to throwing it in the trash and getting a different brand. I still do some consulting work and need to find a controller that has solid homekit support. I’m already advising people to stay away from the rachio.