I am a regular user of Ubuntu. I recently moved on from Ubuntu 19 for 20.04 LTS, but after the upgradation the settings is not opening. Besides the settings the display settings and change background option are not working also,
Your Gnome-Control-Center might need reinstalling. Open your terminal and enter these commands:
sudo apt-get update sudo apt-get install --reinstall gnome-control-center
And then the commands for opening the display and system settings, respectively, would be:
gnome-control-center display gnome-control-center
These commands will change the desktop background: First, get the URI of the background image:
gsettings get org.gnome.desktop.background picture-uri 'file:///home/yourusername/Pictures/yourpic.jpg'
Then set the background URI like so:
gsettings set org.gnome.desktop.background picture-uri 'file:///home/yourname/Pictures/yourpic.jpg'
And it will update your desktop background.
Best of luck!
I had a similar problem where settings would not open after an upgrade. All the updates appeared to be installed, none of the above from Ollie worked. Eventually found it was a window/screen/display problem. Try pressing "shift + win + left arrow" or similar combinations to switch displays to where the settings app is open but not visible. Then you can try a single display - I found it was set to "join" which clearly didn't work.