I might ve found the problem in my Z2M

[slow lodge]

Yes, t needs to be the IP of the host (or if you're running Mosquitto in the same Docker stack you can use the name of the container) and the port, eg

server: mqtt://mosquitto:1883

You also want to use authentication on your broker.

And yes, don't use permit_join: true that's Bad ™️

[chilly pond]

Thanks for your help dude 🙂 yeah that server was a mistake and I did instantly change the permit_join to false 🙂

I just went through the whole installation again, saw I had 2 different mistakes in the config file in zigbee2mqtt and now it all works