Hello Jon and CliveS,
Jon, not willing to derail your plans, but... have you seen sections d) and e) of the following link?
https://github.com/xAPPO/MQTTIn there the author of the xAPPO/MQTT App and Driver for Hubitat Elevation provides some info on **automatic** discovery of devices (therefore, not needing virtual devices) in his App.
Like I said before, I found some of the documentation available for the MQTT App and Driver kind of lacking/confusing, but I thought I should give you this pointer, as my understanding is that there are two methods for automatic discovery of "foreign" devices into HE:
a) one is to import devices from Homie and/or OpenHAB, by using something called the Homie3 protocol.
b) the other is to import devices from HomeAssistant, by using another thing called the statestream protocol.
I had no idea neither of those existed before I first learnt about the xAPPO/MQTT App and driver.
What I'm trying to do using Joe's MQTT Connector is using triggers that add MQTT data that tries to follow the Homie schema, so the automatic discovery already built on xAPPO/MQTT App will go on and populate the dropdowns existing on the section of MQTT App depicted on my previous screen grab. From there, I figure I should choose the devices I want the App to create. At least this is what I figure is possible. If I can't make it work using the Homie schema until tomorrow, starting Monday I will try the same thing using the HomeAssistant schema.
So, if you still have not seen section d) and e) from above linked github, maybe you could and see if your understanding is the same as mine.
Your last post here seem to indicate you are thinking of doing something more in line with what is explained in section f) of the above linked github.
Best regards and many, many thanks for all your help.