RC radio setup not working for heli airframe

Hi there,

I’m currently facing the issue that the radio control is not properly shown in QGroundControl (QGC).
e.g. only with a certain power cycling I get the channel monitor in QGC showing up for calibration. I also can get this working by luck and if I am using a default quadrotor airframe.

Now I am actually interested in using the standard helicopter airframe to build a helicopter drone. With this airframe, I do not get any channel monitor working.
Do you have an idea about possible causes or hints how to proceed?

I’m currently using the latest stable version of QGroundControl, a Holybro PixHawk5X with latest stable firmware, a Futaba T8J radio control and a Futaba R2008SB receiver with S.BUS connection.
RC receiver and control are properly linked, and the RC receiver is working (e.g., attaching a servo directly to the RC receiver is working correctly).