You don’t have to use the MQTT 2 binding. If this was working before, just uninstall it, make sure you have “Show Legacy 1.x bindings” enabled in PaperUI’s configs. Then reinstall the MQTT1 binding.
Perhaps explain what wasn’t clear about those explanations. At this point, those explanations are it. They are all that exist.
MQTT is a pretty low level binding. Whether you think it’s fair or not, but you are going to have to work on working through documentation like this even as a non-programmer. Because it is so low level, it is never going to be as easy or simple to use MQTT as, for example, zwave. This goes double so for a user who insists on not using the UIs to manage Things.
In general, the developer of the MQTT2 binding is only really interested in supporting management of Things in PaperUI. So if you don’t want to use PaperUI you will not have as much support. But there are tons of examples for how to define the Things in PaperUI. I myself don’t use .things files but only PaperUI (and have never experienced any problems with Zwave, you should open a new thread on that problem).
You don’t need an event bus for just two Items. It would be much easier to just configure MQTT Generic Things on both instances to publish/subscribe to the same topics so updates and commands in one get published and update or commands the Items in the other.
There have been many generic tutorials posted to the forum on how to set up MQTT 2.4 including:
- Shelly1 and mqtt 2.4.0 Binding
- My MQTT 1.x to 2.x Migration Experiences
- Migrating MQTT1 items to MQTT2.4 items
- Using MySensors and openHAB2 MQTT2 binding (has an example for how to write the .things files)
- Set up mqtt2 from scratch on linux (more examples, look in the thread below the original posting)
- Using Sonoff Power Switches with Tasmota firmware and openHAB2 MQTT2 binding
and so on.
It’s worth noting that the 2.4 version of the binding has some bugs with .things files that will require a reboot of OH every time you make a change. You should upgrade to OH 2.5 V1 if you plan to use .things files.
To reproduce the event bus behavior there is some documentation here.