Nuitka has its own types for compiled method and compiled function.
The compiled method has the same attributes as a method, and the compiled function the same attributes as a function in CPython. The only difference is that PyFunction_Check and PyMethod_Check will not pass.
I have ventured into PySide and Shiboken and found all occurrences of these and prepared patches to allow for compiled methods and functions as well.
I will upload my patches once I successfully tested them.