Plasma 5.6.5 and Frameworks 5.23 have hit the Backports PPA people!
Plasma 5.6.5 brings bugfixes and translations from the month of June thanks to contributors, while Frameworks 5.23 brings new fixes in KWallet, KWayland, Breeze and much more!
Plasma: https://www.kde.org/announcements/plasma-5.6.5.php
Frameworks: https://www.kde.org/announcements/kde-frameworks-5.23.0.php
To update, use the Software Repository Guide to add the following repository to your software sources list:
ppa:kubuntu-ppa/backports