Unfortunately in my hands it doesn’t work as Mtpaulsen has made it work. Changing the device handler did, exactly once, put a value to the current wattage. It never updated, nor did it correctly (or at all) count power consumption. I have the impression that it is not following Zigbee standards (except for on/off), but instead uses the Tuya cluster to communicate. When I have time, I will try to investigate that in more detail.
For the time being, may I ask whether anybody has already made it work, and if so, how exactly?