Back to the topic at hand, if you’re using Ubuntu 20.04 and want to use multiple workspaces with multiple monitors, the default behavior is to only switch workspaces on your primary monitor. This is less-than-helpful.
Enter one of my favorite add-ons for Gnome, Gnome-Tweaks. You can install it by opening a terminal and typing:
sudo apt install gnome-tweaks
Then launch it by typing gnome-tweaks in the terminal or by hitting your “super” (ie. Windows) key and searching for “tweak”.
Once it’s open, click on “Workspaces” on the left and check “Workspaces span display” under the “Display Handling” header … that’s all there is to it!