If the package appmenu-qt5 is installed, Plasma is broken. This is due to appmenu-qt5 installing a /etc/profile.d/appmenu-qt5.sh which sets the QT_QPA_PLATFORMTHEME env variable. By having that loaded into the session the qpt plugin provided by plasma-integration won't be loaded. Ideally this should be fixed by appmenu-qt5, but so far this hasn't happened: https://bugs.launchpad.net/appmenu-qt5/+bug/1434516 Reproducible: Always Steps to Reproduce: 1. Install appmenu-qt5 2. Try to use Plasma Actual Results: Plasma broken, e.g. breeze not loaded as widget style Expected Results: Plasma working correctly
http://packaging.neon.kde.org/cgit/plasma/plasma-integration.git/commit/?id=4940be210fe602835e11cb8826d08f1bcac0cf6f