Comment # 5 on bug 1010880 from Christos Gourdoupis

This is truly a bug, and sddm, kde or X are irrelevant.
I read somewhere that the feature was dropped because it was causing trouble in
laptops lacking numpads.
Some of us are still using desktops and even more astonishingly the virtual
terminal.
A work around is to add the following to boot.local (which btw is also
deprecated)

for tty in /dev/tty[1-9]*; do
    setleds -D +num < $tty
done