Hello, I seem to have the same issue: due to OpenZwave being deprecated in domoticz, I have been requested to migrate to zwave-js-UI and MQTT.
To that end, I have installed both on my Raspberry Pi3 b+, however NOT using docker-compose because this tutorial
https://wiki.domoticz.com/Zwave-JS-UI did not work for me regarding Mosquitto for some reason I still can't figure-out, so I installed mosquitto simply using apt-get install mosquitto (and kept docker for zwave-js-ui).
The mosquitto broker service seems to work (service status showing as "active", MQTT-explorer showing the tree of devices) and so does Zwave JS UI at 192.168.1.xx:8091 (e.g. showing the connectivity of devices with proper names, and all devices are reported as "alive").
In Domoticz, I have installed the "MQTT Auto Discovery Client Gateway with LAN interface" hardware under "setup - H/W". The H/W is "enabled" and if I click "setup" next to this H/W, I see a bunch of nodes (that have no sensible names).
Now, and this is the problem, if I go to the "device" section of domoticz, I can't see any new device that is attached to a Zwave controller. So in effect I can't use the devices...
I spent the entire day trying to figure-out to no avail, however I must confess I'm not used to managing this environment.
I'm not sure if this is a Domoticz issue or a MQTT issue, or more likely just a configuration that I mismanaged while installing those applications and services. Please note that I did enable MQTT gateway in Zwave-js-ui, and I double checked the local host IP address, discovery prefixes, port numbers, etc.
I would be happy to receive some help here. Maybe it's something obvious !
Thanks a lot,
Manu