When you get a taste for the virtual desktop under Linux, it's quite difficult to do without it.
On Ubuntu 18.04, by default, when the user change his virtual desktop with a multi-screen configuration, only the primary screen change ! To modify this comportement and change the desktop on all screens, you must check the value of a global setting value, with the following command in a terminal:
gsettings get org.gnome.mutter workspaces-only-on-primary
If the response is false
, check the options of your graphics drivers. You may have missed a option.
If the response is true
, type the following command to extend the changement on all screens:
gsettings set org.gnome.mutter workspaces-only-on-primary false
That's all !