How to check if MQTT is working

I have Diyhue running on my Synology in Docker using a macvlan. I have now also configured MQTT in the webui to connect to my Mosquito instance. I have Z2M and Mosquito running already for HA. I can connect my Philips Hue light to Z2M and see them in HA but can’t get Diyhue to detect them.

I’m not sure Diyhue is successfully connected to Mosquito. How can I check that?