Finally I found some time to buy some Arduino and test it. Basically it works. I've got a list of Mav2Duplex sensors in my sensors list where I can choose which ones I want to get displayed.
Most important for me is battery voltage and GPS satfix and both work fine. However, number of satellites doesn't work, it always indicates 255. Also nav height remains at 0.0m but I'm not yet sure if it's the relative height to the ground while flying in any mode or if it only displays height while navigating.
Compared to the Mav2Hott it seems poorly equipped but it offers me all I need. While testing with my Graupner radio, I never used the waypoint editor because editing waypoints with my android tablet is much more comfortable.
Main (flight) display:

List of available parameters:
