For people wanting onboard (virtual keyboard) in the lightdm-greeter, which is a handy feature to have around for touchscreens as well is for broken keyboards.
Configure " /etc/lightdm/lightdm-gtk-greeter" as root with sudo. i.e " sudo nano /etc/lightdm/light-dm-greeter".
Go to the end of the file under [screen] and remove the # and add " onboard" behind " keyboard="
thus:
Save it and on next login you' ll have the option added to the top right menu.
thus:
I think it would be even better if @Thanatermesis configered the greeter this way by default, seeing as " onboard" is now installed by default too.