Tested with the snapshot from 27.07.2021.
Trying to debug a qmake + Qt 6 application did not work; neither on an Android 10 Smartphone nor on an Android 11 Tablet (with USB debugging enabled).
It resulted in the following output in the "Application Output" pane:
killall: gdbserver: No such process10:31:20: Unable to create a debugging engine.
I libc : SetHeapTaggingLevel: tag level set to 0
I .example.affin: Late-enabling -Xcheck:jni
I .example.affin: Unquickening 26 vdex files!
D ActivityThread: setConscryptValidator
D ActivityThread: setConscryptValidator - put
D ActivityThread: handleBindApplication()++ app=org.qtproject.example.affine
W ActivityThread: Application org.qtproject.example.affine is waiting for the debugger on port 8100...I System.out: Sending WAIT chunk
10:31:20: "org.qtproject.example.affine" died.
Running the application normally (started from Creator) worked; basic adb functionality like logcat worked too when invoked from the command line..