This relates to Is it possible to embed C++ widget to PyQt application?.
This is basically the same question, only that the newer versions of SIP have changed their configuration method so the great example given in the original question is deprecated now.
I am looking for a minimal example that works with the current version of SIP 6 and explicitly works with Qt.
There is a minimum example for general bindings at https://www.riverbankcomputing.com/static/Docs/sip/examples.html#a-standalone-project, but I am stuck at making the leap to actually bind C++ code that contains Qt.