The Kubuntu Backports PPA for 21.10 contains newer versions of KDE Gear and other KDE software. The PPA will also continue to receive updated versions of KDE packages other than Plasma, for example KDE Frameworks.
To upgrade, add the following repository to your software sources list:
ppa:kubuntu-ppa/backports
or if it is already added, the updates should become available via your preferred update method.
The PPA can be added manually in the Konsole terminal with the command:
sudo add-apt-repository ppa:kubuntu-ppa/backports
and packages then updated with
sudo apt full-upgrade