PyQt5 does not seem to be maintained. The last couple of times I checked it, it was pretty dead: one maintainer with no time.

I think you have this backwards. PyQt5 is well maintained by a company that produces a GPL version and sells a commercially licensed version, which was Qt's original business model. Pyside was originally created by Nokia back when Nokia bought Qt, re-licensed it as LGPL, and needed LGPL python bindings. It's no longer maintained and only works with Qt4. Pyside 2 is a port of pyside to Qt 5 that seems to have some level of activity, but no releases..

Templatize the language, toolkit version and that could just about describe every binding of every c++ toolkit ever made.

I think the Qt Company is trying to revive pyside, but they have a lot of catching up to do. Not sure if they plan to do an update on their bindings generator (Shiboken) too, or start from scratch on that front.

Yes, I actually do have this backwards .. in more than one way ..:P

Sorry, I was thinking of Lua for Qt5 .. That was silly!

And, it is a pity about PySide, it was a neat project. :(