How to fix the system tray widget?

Error loading QML file: file:///usr/share/plasma/plasmoids/org.kde.plasma.private.systemtray/contents/ui/main.qml:375:19: Type ExpandedRepresentation unavailable
file:///usr/share/plasma/plasmoids/org.kde.plasma.private.systemtray/contents/ui/ExpandedRepresentation.qml:133:5: PlasmoidPopupsContainer is not a type

You on Debian testing? If so, this forum as well as the general ecosphere is full of bug reports, solutions and workarounds. In a nutshell, you need to get a package (I cannot remember which) from unstable.

Until yesterday, Plasma on Debian testing was broken because Plasma 5.13 landed in testing before Frameworks 5.49, used to build it.

Now it solved (the solution was "get *all* Frameworks package from sid). It should have been fixed with yesterday's updates.

If you are not on Debian testing, you should state which distribution and version you use and other details which can be used by other people to help.

Thank you for the tips and tricks.

Looks like 'installpkg --root /kde5dir packagename' is causing the error.