Not able to change the Nvidia driver in ubuntu 20.04

Solution 1:

This problem should be fixed by running

sudo ubuntu-drivers autoinstall

after a reboot.

Solution 2:

I encountered myself in a similar situation because of broken packages (Ubuntu complained on launching sudo ubuntu-drivers autoinstall; further in Software & Updates -> Additional Drivers my Nvidia graphics was locked to manual installation). I solved it like this:

1. Remove all nvidia packages and make sure nouveau is installed (you need sudo rights):

dpkg -P $(dpkg -l | grep nvidia-driver | awk '{print $2}')
apt autoremove
apt install xserver-xorg-video-nouveau

2. Reboot
3. Reinstall latest nvidia packages (again, sudo rights):

ubuntu-drivers autoinstall