msp-osd not showing up (INAV 6.0)

[MomoRC-tech]

Devices/setup:

• FC: Diatone Mamba F722 APP

• Goggles V2, FW v1.00.0606
  Trace ID: 32a1bdf7-c8cd-4cb9-b65f-b86308c1c0aa

• DJI Airunit FW v1.00.0606

• INAV 6.0

• rooted v2 goggles/airunit, installed wtfos and packages (msp-osd)

• standard INAV "DJI FPV VTX" serial port config for custom OSD is working
  --> serial port wiring seems correct

Describe the issue

• INAV: switched to "MSP Displayport", enable HD OSD, "DJIWTF"
  --> msp-osd seems not to work as no OSD elements are showing up

Please give debug hints:

• how to debug if MSP messages are received in the air unit msp-osd part?
• how to debug if there is according data inflow in the goggles SW?

[relaxibus]

Did you verified UART TX/RX wires? May be swap them. It sounds like no UART data are received by the VTX.

[MomoRC-tech]

UARTS are OK, as there ist the reduced OSD Info shown when I set this UART to "DJI VTX"
Is there a SW debug possibility in the Airunit to verify incoming messages?