On afresh install Ubuntu 20.04 with the NVIDIA graphic card Geforce GF108M [GeForce GT 620M/630M/635M/640M LE], the HDMI output is not working and the driver seems not to be working.
ubuntu-drivers devices
== /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0 ==
modalias : pci:v000010DEd00000DE9sv00001043sd00001477bc03sc00i00
vendor : NVIDIA Corporation
model : GF108M [GeForce GT 620M/630M/635M/640M LE]
driver : nvidia-driver-390 - distro non-free recommended
driver : nvidia-340 - distro non-free
driver : xserver-xorg-video-nouveau - distro free builtin
There are two missing dependencies : xserver-xorg-video-nvidia-390 and ibnvidia-cfg1-390
This command failed on a fresh install for Ubuntu 20.04 with a
sudo ubuntu-drivers autoinstall
There were 2 missing dependencies : xserver-xorg-video-nvidia-390 and ibnvidia-cfg1-390
Installing both manually
sudo apt-get install libnvidia-cfg1-390
sudo apt-get install xserver-xorg-video-nvidia-390D
sudo ubuntu-drivers autoinstall
sudo reboot
solved the issue. Hope this can help.