I have the same problem, its not supported in stable release and I hesitate to update my domoticz to beta version....
So we will have to wait for the next stable version.

Any change there will be a beta version for my Synology 215+ to be able to handle my Xiaomi devices better? I have added a Xiaomi gateway to my domoticz, its working except that I get "XiaomiGateway: unhandled model: sensor_motion.aq2" from my motion sensor. Or is there a possibility to manual add ...