Premiering in KDE Plasma 6.7 was Union as the new CSS-based style/theming engine for Plasma. Union ultimately aims to address KDE's fragmented ways of styling apps. As a step closer to that goal, there is now the initial release of Union for QtWidgets support.

KDE developer Akseli Lahtinen announced today the initial release of Union QtWidgets so that QtWidgets-based apps like the Kate editor, Dolphin file manager, etc, can now use Union CSS files for styling. There are some known styling issues at the moment with some aspects being off and the like, but they are being worked on. The expectation is this Union QtWidgets support will be part of the upcoming KDE Plasma 6.8 release.

Lahtinen noted in his blog post:

"This is the first time ever Breeze QtWidgets and QtQuick style have same shared source-of-truth as an easily editable file! (Excluding colorschemes.) So some of these designs are made with QtQuick in mind, so they can look a bit off in QtWidgets."
Those wishing to learn more about this milestone can do so via this blog post.