Thanks for the hint, but I checked this before.
For the sensors, I found a solution in another thread: [SOLVED] Rule to show window as open or closed when wifi contact sensor sends RF data - #53 by ngalfas
Now it works as:
Type contact : TestReceiver1 "TestReceiver (2)" [
stateTopic="openHAB1_RFBridge2/tele/RESULT",
transformationPattern="JSONPATH:$.RfReceived.Data",
on="F27322", off="F27324" ]
without having to define a separate Map or JS transformation for each channel. So @ssmall, you should try again with your first approach. Maybe there was a handling problem or a bug in the binding, when you tried it first.
However, the warning still shows, if a code is received which is not covered by the two switch states. This will clutter my log, when I will have all sensors configured for MQTT2. So I am still open for an even better solution.
My next step will be to find a way to have a momentary button to trigger ON and OFF states, but I did not find yet a way to use system channel types with MQTT binding.