You are right, I am indeed using Kicker and not Kickoff. Sorry for messing up
the two and thanks for correctly identifying that. :)
The icon is correctly shown when running Kicker in plasmawindowed. I also don't
see anything obviously related in the log messages in that case:
> plasmawindowed org.kde.plasma.kicker
Loading default layout
QObject::disconnect: Unexpected nullptr parameter
kf.plasma.core: requesting config for "Anwendungsmen���" without a containment!
kf.plasma.quick: Applet preload policy set to 1
Entry is not valid "writer.desktop" QSharedPointer(0x1874500)
Entry is not valid "org.kde.khelpcenter.desktop" QSharedPointer(0x1946090)
trying to show an empty dialog
trying to show an empty dialog
qml: 0
Entry is not valid "writer.desktop" QSharedPointer(0x2674fe0)
Entry is not valid "org.kde.khelpcenter.desktop" QSharedPointer(0x2675320)
Entry is not valid "writer.desktop" QSharedPointer(0x2674b80)
Entry is not valid "org.kde.khelpcenter.desktop" QSharedPointer(0x2674e30)
libpng warning: iCCP: known incorrect sRGB profile
trying to show an empty dialog
trying to show an empty dialog
trying to show an empty dialog
kf.plasma.core: requesting config for "Anwendungs-Starter" without a
containment!
Trying to use rootObject before initialization is completed, whilst using
setInitializationDelayed. Forcing completion
qml: 0
trying to show an empty dialog
libpng warning: iCCP: known incorrect sRGB profile
trying to show an empty dialog
Now knowing about the difference in Kickoff and Kicker, I have also explicitly
tested Kickoff. It shows the same behaviour, the Icon is not shown in the
favourites section but does show in search results and when running via
plasmawindowed.