Oh you thought your Linux desktop is free? Your KDE Plasma installation is not activated, go to Settings to activate it.
Inspired by https://github.com/isjerryxiao/gnome-shell-extension-activate-gnome
Directly from GitHub:
git clone https://github.com/RedL0tus/Activate-Plasma activate-plasma
cd activate-plasma
kpackagetool5 -t Plasma/Applet --install fish.salted.activate-plasma