After an apt-upgrade, my KDE dock/task manager icons in Kubuntu are all black [duplicate]

I recently ran do-release-upgrade to upgrade to Kubuntu 21.04 from 20.04 without issue. Other than some (expected) differences in configuration files, nothing failed. When I logged in to plasma, I was surprised to see all the sys tray's icons have been replaced with black placeholder squares -- see screenshot below. This is true even in alternative widgets, and in the the application launcher (all the icons are black squares).

There's nothing obvious in /var/log/syslog and I have an AMD gpu, which can happily run glxgears. The closest thing to a relevant error message is

Jun 14 22:01:49 localhost org.kde.KScreen[6021]: kscreen.xcb.helper: Event Error:  147

I'd love some help debugging this. Does anyone have any ideas? Should I report this to the devs, or will I be a hindrance?

Solution 1:

Mods, feel free to close this -- apologies; it is a dupe of this question (albeit in disguise!): Black icons after reinstalling Kubuntu desktop

A quick installation of sudo apt install libqt5quick5 fixed the problem. Do'h.