KDE Plasma icons showing in UBUNTU DESKTOP

When you installed KDE plasma, it also installed the KDE icon theme (breeze). You need to use Gnome Tweaks and set your Icons again to the default Ubuntu Icon theme (Yaru).

  1. Install Gnome Tweaks to configure your icon theme:
    sudo apt-get install gnome-tweaks 
    
  2. Open Gnome Tweaks:
    sudo gnome-tweaks 
    
  3. Navigate to appearance --> Icon --> Yaru
  4. Save the changes and quit gnome tweaks.
  5. Log out and Log in again to prevent lags.