How to Configure a Static IP Address in KDE Plasma
Configuring a static IP address with the KDE Network Manager is fairly straightforward. It's a good way to lock down a single IP address for a specific machine so it never changes (until you change it). How do you make this happen? With the KDE Network Manager (otherwise known as Connections).
https://www.lifewire.com/how-to-configure-networking-in-kde-plasma-4683939