QUiLoader does not connect signals/slots connections with Python types

When creating a UI file with Qt Designer, it is convenient to promote native widgets in order to use custom widgets, to add their signals and slots and to use the signals & slots editor in Qt Designer to connect the various signals and slots of native and / or custom widgets.

Unfortunately, importing a UI file directly fails to properly connect the signals and slots as declared in Qt Designer. Converting the UI file into a Python class works properly (see the two ways of using a Qt Designer-made UI file in the documentation). It seems that the QUiLoader used in direct import may be failing.

I have created a minimalistic example on GitHub which files I will attach here as well.