i3 WM with KDE
Use of the i3 as the window manager instead of Kwin can be done in the following way.
Create a file at:
/usr/share/xsessions/plasma-i3.desktop
With the following content
[Desktop Entry]
Type=XSessions
Exec=env KDEVM=/usr/bin/i3 /usr/bin/startplasma-x11
DesktopNames=KDE
Name=Plasma with i3
Comment=Plasma with i3