OH3+MQTTBroker+CC2531 problem

What have you setup to make this work automatically? By default, using zigbee2mqtt means you have to manually add your devices into openHAB.

Here’s how I setup a ZigBee bulb into openHAB 3 via zigbee2mqtt:

And here is a switch into openHAB 2 via zigbee2mqtt:

Zigbee2mqtt now also has a web interface so setup of zigbee2mqtt is even easier than shown in those tutorials, but they should get you the basics.

I highly recommend installing MQTT Explorer and connect it to your MQTT Broker so that you can see all the messages that are published.