As the journal shows, there are many errors, leading to the kuiserver failing to load, thus no proper Plasma is loaded.
Dolphin shows many errors related to inotify_add, example:
sep 23 06:54:59 <HOSTNAME> dolphin: inotify_add_watch(/run/sudo) failed: (Permission denied)
leading to the kuiserver failure.
If you don't use any encryption, then make sure to test with a new, clean user, could very well that one of your settings/themes/plasmoid is not ready for new Qt.