Hi Helmut. Xaos started this Qt6/QMake6 discussion and turned out to be a good testbed for checking debhelper versus Qt6 compatibility.
A someone pointed out (sorry cannot find his name browsing on the phone), the generic first thing to try would be to try CMake instead. But I don't want to deprive you of an opportunity to improve debhelper. I cannot upload either for now and dont want to stall you so please ask the games team. I will review all your other FTBCS bugs in 2024. Greetings