As of 10.6.2, the Python binding can be done as part of the main Geant4 build. Apologies that this wasn’t updated in the docs. To enable it, build Geant4 as per the install guide, but add the option
-DGEANT4_USE_PYTHON=ON
This requires Python 3, plus Boost with Python3 support. If you want Geant4 built in Multithreaded mode with Python, this will also require the options:
-DGEANT4_BUILD_MULTITHREADED=ON
-DGEANT4_BUILD_TLS_MODEL=global-dynamic