I just got these as well this week. I looked at those webpages and they seem to give good instructions but there is no firmware that I can find that works beyond Dohomes. The website give some instruction on how to create firmware but that is beyond me. It appears to use Esp8285 and can be upgrade OTA but just no firmware yet.
I think I’ll focus on getting it paired with HA homekit controller.
I will use this method to get homekit devices to operate in HA in the mean time.