Here some tips that might help you:
- First site to check is zigbee2mqtt.io and search under devices. There you can see all attributes and how they are exposed
- I recommend to switch zigbee2mqtt to attribute mode so that each attribute is transfered seperately and not as a single json. Everthing is described here with lots of examples https://community.openhab.org/t/zigbee2mqtt-revisited-no-more-ugly-transformations/86362. Your plugs should work just like the OSRAM-examples
- Another way is to use the autodetect feature of the mqtt-broker in openhab. You can switch it on by turning on “show advanced” in your mqtt-thing and then at the bottom “discovery”. It doesn’t work perfectly with all kinds of devices but maybe it’s an option for you.