There is no support for the XKB extension now. You can find the list of available extensions here:
https://github.com/python-xlib/python-xlib/blob/master/Xlib/ext/__init__.py

This project is just being maintained with bug fixes, but PRs with support for additional extensions (or other features) are always welcome. If you want to have a stab at it yourself there's unfortunately no documentation on how to implement an extension, but you can have a look at some of the existing ones, e.g. https://github.com/python-xlib/python-xlib/blob/master/Xlib/ext/dpms.py

Extensions do not work in the same way as in the C Xlib, so there will not be an equivalent of XkbOpenDisplay. Instead methods are added to the Display and other X objects directly, once the display connection have been open and it's known which extensions the server supports.

I will give it a shot by the end of this month, I'm a little overloaded right now :)