It says: "The system must be restarted to fully to apply ..."
Oops.
Git commit c7d4b22f82e1d07e78322d26b0e856d468e18994 by Nate Graham. Committed on 09/08/2021 at 18:08. Pushed by ngraham into branch 'master'. Correct typo in update reboot message FIXED-IN: 5.23 M +1 -1 discover/qml/UpdatesPage.qml https://invent.kde.org/plasma/discover/commit/c7d4b22f82e1d07e78322d26b0e856d468e18994