Raspi3+, Buster, OpenHAB2, Mosquitto, Sonoff Basic-Tasmota, all paper UI configs.
Installed nicely, and have Philips Hue lights working well.
Installed Mosquitto and it is up and running.
Tasmota’ed a sonoff basic and that went well.
I can control the sonoff (as in on and off) via http (192.168.86.29/cm?cmnd=Power%20Off).
However!
When I toggle the OpenHAB2 switch it shows the switch changing from OFF to ON
The sonoff showing a stat/tasmota_A017D/POWER
and MQTT Explorer showing a stat, but no cmnd
So, OpenHab is communicating with Mosquitto, and Mosquitto with the Sonoff. Hence I feel i have a command config problem.
Your systemBroker Thing is not what you think it is, all.
It’s a bridge for cummunication between openHAB and the embedded (moquette) broker, for admin purposes, like broker settings.
It’s of no use at all for MQTT messages to/from external devices.
You may have named it mqtt:systemBroker:mosquitto but it has nothing to do with your actual mosquitto broker.
So in PaperUI, delete that Thing, uninstall the (misc) Embedded MQTT Broker if you have it
Start over by adding an MQTT Broker Thing to your MQTT binding, point that at your Mosquitto.