Gottfried Haider made a great integration to HomeKit that allows AirGradient monitors to send data directly to Homekit. We tested it and can confirm that the version works great on the PCB v 3.7.
At the moment the example sketch in the repository only supports the older pro diy version 3.7. But it should be relatively easy to copy the specific sections to the newer versions as well.
It supports all five air quality parameters that the DIY Pro gives you. PM, CO2, TVOCs, NOx, Temperature and Humidity.
It is important that you follow exactly the steps outlines on the repository page under usage. There are some very specific settings mentioned that could easily get overlooked. You also need to first download the Arduino HomeKit Library version 1.4.0 from its github. Do not install it from the Arduino library manager because the one on github is a newer version.
We would like to say a big thank you to Gottfried for creating this very cool integration. If you have any specific questions or problem, please reach out to him or head over to the AirGradient Forum for discussion.