This web site:
https://www.techotopia.com/index.php...top_Background
Tells me to right click anywhere to change the background. I have a Logitech mouse, MX 500, with two left side buttons, a roller, then three buttons above and below the roller. Right click does absolutely nothing. Windows does recognize that button.
Click
and there are no options for setting mouse buttons. The Help option there does not mention buttons other than setting for right or left handed moussing.
The goal was to set the wallpaper. However, there is apparently a more immediate problem of configuring the mouse. What can be done to convince Centos that the mouse has a right side button.

Did you try all the buttons to see if any of them are right click.

When Firefox is open and displaying an html file, a right click opens a dialog with a list of options such as: save page as. So I have a high degree of confidence that the Centos drivers recognize a mouse right click.

That page doesn't say right click "anywhere" -- it says on the "...current desktop background"...to get the background change dialog.

And this is a Gnome issue, not a CentOS issue.