SDDM

Simple Desktop Display Manager (SDDM) is a display manager supports X11 and Wayland.

Emerge
Install :

Without systemd
If you see performance issues, it might help to add the sddm user to the video group.

Configuration
The configuration file for SDDM is:

Boot service
To start SDDM on boot:

To start SDDM now:

Plasma
Graphical configuration is integrated in Plasma 5 system settings by installing :