This worked for me and might not work for your.
Try it at your own risk!
Add the neon repositories and install the neon desktop
$ wget -qO - 'http://archive.neon.kde.org/public.key' | sudo apt-key add - $ sudo apt-add-repository http://archive.neon.kde.org/user $ sudo apt-get update $ sudo apt-get install neon-desktop
Upgrade everything. Repeat if necessary, until everything is really up to date and you have no held-back packages.
$ sudo apt-get update $ sudo apt-get upgrade $ sudo apt-get dist-upgrade