Just for clarity, I stopped trying to build with python3 and went back to python 2.7 interpreter since the displayCAL program requested from the beginning of their documentation that it requires python 2.7. I used wxPython 4.1.0
I run to this problem https://discuss.wxpython.org/t/building-wxpython-4-1-0-nixpkgs/34706 which seems unsolved from 2020 so I suppose I will stop looking into it too.