I am hit also by this, e.g. no systray or alt+f2 not finding anything. Running with a local built packages of src:plasma-workspace (in a just testing packages environment) the systray came back and alt+f2 is also normal again.
Hello,I am also affected by this problem and I can also confirm that, as Bernhard says, building plasma-workspace with deb-src and installing the built package (plasma-workspace is enough, disregard all other created packages) brings everything back to normal.
Regards, Iacopo