ubuntu on pi 4

[Kyle]

Lightdm needs the slick greeter in order to work correctly with Orca. I 
believe Ubuntu may be using the gtk greeter, which requires manually 
editing a configuration file in order to get the screen reader talking, 
unless they fixed that in Ubuntu. I know there is a long-standing 
Launchpad bug for this. if alt+super+s doesn't start Orca at the lightdm 
screen as expected, it is starting lightdm-gtk-greeter rather than 
lightdm-slick-greeter. Perhaps the easiest way to fix this would be via 
ssh, running something like

sudo apt install lightdm-slick-greeter

sudo apt remove lightdm-gtk-greeter

Hope this helps.

~Kyle