Experienced the same bug with the same behavior and more:

• the entire System Tray disappeared except the clock widget
• all the program's widgets he task bar disappeared also
  In my opinion the bug's severity is more than "minor".
  Hope the issue will be fixed soon.
  Thank you and best regards

I have this issue as well. You can reproduce it easily by downloading the latest kali-linux-kde-2018-3-amd64-iso and simply doing apt update && apt upgrade and rebooting. Plasmashell 5.13.4 seems to be the problem.

Some output when plasmashell is run:

org.kde.plasmaquick: Applet preload policy set to 1
org.kde.plasma: Applet "org.kde.plasma.systemtray" could not be loaded.
org.kde.plasma: Applet "org.kde.plasma.notifications" could not be loaded.
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:61:28: Unable to assign [undefined] to int
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:52:27: Unable to assign [undefined] to int
kf5.kpackage: No metadata file in the package, expected it at: "/home/REDACTED/Pictures/"
kf5.kpackage: No metadata file in the package, expected it at: "/home/REDACTED/Pictures/"
kf5.kpackage: No metadata file in the package, expected it at: "/home/REDACTED/Pictures/"
trying to show an empty dialog
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
qml: onLoaded
qml: bindSignals ICalManager_QMLTYPE_151(0x55c3bfe630e0)
qml: bindSignals DebugCalendarManager_QMLTYPE_149(0x55c3bfe651e0)
qml: bindSignals GoogleCalendarManager_QMLTYPE_148(0x55c3bfe65fe0)
qml: bindSignals PlasmaCalendarManager_QMLTYPE_152(0x55c3bfe67220)
qml: bindSignals ICalManager_QMLTYPE_151(0x55c3bfe374b0)
qml: bindSignals DebugCalendarManager_QMLTYPE_149(0x55c3bfe474d0)
qml: bindSignals GoogleCalendarManager_QMLTYPE_148(0x55c3bfe52310)
qml: bindSignals PlasmaCalendarManager_QMLTYPE_152(0x55c3bfe57a70)
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
qml: disabling redshift
qml: renderModeString:
qml: disabling redshift
trying to show an empty dialog
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
trying to show an empty dialog
Both point size and pixel size set. Using pixel size.
QFont::setPixelSize: Pixel size <= 0 (0)
trying to show an empty dialog
QFont::setPixelSize: Pixel size <= 0 (0)
QFont::setPixelSize: Pixel size <= 0 (0)
trying to show an empty dialog
trying to show an empty dialog
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
file:///home/REDACTED/.local/share/plasma/plasmoids/org.kde.plasma.bitcoinprice/contents/code/bitcoin.js:71: SyntaxError: JSON.parse: Parse error
qml: clearing connected sources, stop source was: killall redshift; redshift -x
qml: enabling redshift with command: redshift -l 35.9543:-93.9795 -t 6500:4000 -b 1:1 -g 1:1:1
org.kde.plasmaquick: New Applet "Event Calendar" with a weight of 100
org.kde.plasmaquick: New Applet "Bitcoin Price" with a weight of 2
org.kde.plasmaquick: New Applet "KDE Connect Device Widget" with a weight of 92
org.kde.plasmaquick: New Applet "Redshift Control" with a weight of 42
org.kde.plasmaquick: New Applet "Application Launcher" with a weight of 100
Plasma Shell startup completed
trying to show an empty dialog
trying to show an empty dialog
org.kde.plasmaquick: Delayed preload of "Event Calendar" after 0 seconds
file:///home/REDACTED/.local/share/plasma/plasmoids/org.kde.plasma.eventcalendar/contents/ui/AgendaListItem.qml:120:13: QML QQuickText: Detected anchors on an item that is managed by a layout. This is undefined
behavior; use Layout.alignment instead.

Also I agree that this is more than minor. I would say it makes KDE on Kali more or less unusable.

same for me. I honestly think this should be reported to the KDE developers to fix this issue.

Also the same problem. Using KDE is a bit complicated now.

kde-plasma-desktop is imported from Debian upstream. Does this issue occur there as well? I expect this issue is not unique to Kali and will have to be reported upstream to be fixed.

Kali 2018.3 The last update was a chaos. Plasma is updated to version 5.13.4 and QT frameworks is version 5.47 and should be 5.49. Kali KDE is completely unusable. File manager Dolphin does not work, you need to manually update and compile the Dolphin circuit that will not have a root ban

So it looks like that KDE is broken in Debian Testing because it effectively depends on some packages which are stuck in Debian unstable.

See https://lists.debian.org/debian-kde/2018/08/msg00030.html and https://lists.debian.org/debian-kde/2018/08/msg00032.html

I'll try to fetch the packages from unstable and integrate them into kali-rolling.

I migrated all the packages and I'm pushing them out to public mirrors. Let me know if the next dist-upgrade fixes everything for you.

It seems to have solved the problem for me.
Thank you

I have upgraded the system and it seems that those problems are solved.

That fixed it for me as well.

Thanks for the confirmation, closing the ticket then.