I recently tried Plasma 6 (KDE Neon Unstable edition), and installed KVantum. It seems that when I use translucent KVantum theme like GitHub - vinceliuice/McMojave-kde: MacOSX Mojave like theme for KDE Plasma, the windows don’t become blurred. It worked in Plasma 5.
Which project should I report the bug against? The theme? KVantum? KWin?
Has KVantum been ported to work with Qt 6 apps yet? Can you verify that?
Can you try applying it to a QtWidgets app that’s still using Qt5, such as Okular or Kile? Does that work under Plasma 6?
It turns out that blur effects for Qt6 have not been ported to Kvantum yet. Blur does work in Okular.
NOTE: Experimental compilation of Kvantum’s plugin against Qt6 can be done with
cmake .. -DENABLE_QT5=OFF. For now, it lacks blurring support (which requires version 6 of
kwindowsystem). When Qt6 becomes the default version of Qt in some distros, that compilation option will be set to
OFF by default and all components of Kvantum will be compiled against Qt6.