I've been struggling with this all day. My solution (on Ubuntu 20.04) is to downgrade to nvidia driver 435. Change gdm3 to lightdm.
In that exact order
apt install nvidia-driver-435 apt install --reinstall lightdm ubuntu-desktop
The bug is in driver 440. Also confirmed this in Arch Linux as well. gdm still doesn't allow HDMI output even in 435.
I've been struggling with this all day. My solution (on Ubuntu 20.04) is to downgrade to nvidia driver 435.
Change gdm3 to lightdm.
In that exact order
apt install nvidia-driver-435
apt install --reinstall lightdm ubuntu-desktop
The bug is in driver 440. Also confirmed this in Arch Linux as well.
gdm still doesn't allow HDMI output even in 435.