- Edited
Please wait a bit with update/reboot, the icu/boost update started yesterday is still ongoing (didn't upload any for 30 hours to get as much rebuild as needed, but now just uploaded so I can use the buildserver too).
No rebuilds have been done yet in kde-next, waiting for qt6-webengine to build first.
So, yes, your error is known and expected, plasma-workspace6 (among many others) needs a rebuild.
EDIT:
Rebuilds are done, next -Syu will get you the needed packages.