@AverageJoe90
I have not tried contacting them myself yet. They list a phone number on their website.
tel:02477717570
I currently have working Nest Protect units as I added mine to Smartthings prior to Google’s changes. I am also considering using either HomeAssistant or StarlingHome hub to add them to HomeKit.
If however Google conspire to further make integrating them impossible I may explore Fire Angel further. My main concern over Fire Angel is that it looks like either you can get a model which links multiple units together or you can get a model which supports either Zigbee or Z-Wave but not both.
Nest Protect of course does link all the units together. This means when one detects smoke all of them sound the alarm.