I have a dual monitor + laptop screen setup using a thunderbolt dock.
When I try to login to ubuntu with the laptop lid closed it works fine on wayland but with Xorg the screen freezes on the background image until I open the laptop lid, at which point the background will go away and I will get logged in as usual.
If I keep the laptop lid open it works just fine.
I have tried to follow the recommendation at Ubuntu Gnome login screen on ASUS GL552VW with closed lid but it does not help.
