Getting multiple screens independent of each other

[phil.e]

I've got a bunch of users with 3 head systems, running CentOS 7.8.

By default when CentOS installs, you can move windows between screens, and workspaces applies to all monitors at the same time

They want to have 3 independent screens - i.e. you can't move windows between monitors, and each screen has its own separate set of workspaces.

How do you get the independent screens? And what is that called?

[pjsr2]

It is called "extended desktop" when the desktop spans multiple monitors.
The opposite is "multiple displays". So searching for these words may help you find the solution.