Turns out you need to install pip install opencv-contrib-python and not pip install opencv-python. At best make sure you install it in a new enviroment without any old installations.

Here the following two essential functions will be available:

cv.aruco.interpolateCornersCharuco
cv.aruco.calibrateCameraCharuco

I didn't manage to get it working using only the "new" objdetcet module of the non-cotrib version. For a more indepth explanation see here: