Do you use a “firewall” in your knx installation (in german: linienkoppler)?
I don´t need any dummy app inside my ets. You can assign a knx-channel to a device by simply writing it inside the ets, not combine the two things with the mouse pointer.
Example:
I have a presence sensor (non-knx) and this sensor gives a signal to openhab, when movement is recognized. Then openhab sends a “on” message to the knx-adress maybe 5/1/1. I combined my knx-actuator for my lights with this adress inside the ETS and so the light goes on, when there is any movement.
No need for dummy apps.