In Kubuntu 16.04 (with Plasma 5.8) I cannot clone my laptop monitor to an external display. There is a setting "Unify outputs" which will set both monitors to the same resolution, but they are still arranged side by side, and not cloned.
I can clone the output from the command line using something like xrandr --output VGA1 --same-as LVDS1 but it would be nice to be able to do it also from the GUI, the way it used to be possible before 16.04.
It works with HDMI monitors, just not with VGA.