With this I mean a desktop app that renders plain html + css + javascript.
Bit of a hassle to setup everything but PyQT has Python3 support and you can use QtWebEngine with it.
Some times ago I tried kivy but now sure if it can render HTML+CSS. It surely can render canvas objects but I didn't messed with it long enough to answer it exactly.
Peter Scheler
JS enthusiast
An alternative to electron for node is NW.
Something similar for python would be htmlPy.
And here some python onlys.