Switching back from Unity to KDE

Solution 1:

There two ways to proceed:

If your installation of Kubuntu is not corrupted then logout or reboot and select Plasma session on login screen.
If Kubuntu installation is corrupted, then (re)install Kubuntu desktop back by
```
sudo apt-get update
sudo apt-get install --reinstall kubuntu-desktop^
```
While executing above command confirm using SDDM as login screen, then reboot and select Plasma session on login screen.