Comment 5 for bug 1724796

I turned on external PPA because it wasn't working. The problem is simple, image is broken until Xorg is loaded (either by choosing Xorg in GDM, or disabling Wayland for GDM). Xorg does something that fixes the picture in Wayland (and thus in GDM if GDM is running with Wayland enabled).
Some users on irc suggested that this is kernel bug, but I'm not familiar enough with how things work to confirm/test that. I just know that loading Xorg (either as session or GDM) fixes the problem for both sessions.