Comment # 2 on bug 1012289 from Wolfgang Bauer

Sorry, but that is no bug.

The Qt4 settings application is part of qt4 which we still (have to)
ship/install for KDE4/Qt4 applications.

Qt5 doesn't have a settings application, use KDE's systemsettings5 to configure
the look and feel of Qt5 applications.

There is libqt5-qtct too, but that will override KDE's settings, so it's not
recommended to install it if you use the KDE/Plasma desktop.