After upgrading to "groovy" 20.10 from 20.04 via a do-release-upgrade, the mouse scroll wheel no longer switches between virtual desktops. The scroll wheel does work within a window. There were no reported problems during the upgrade. Rightclicking the desktop -> Configure desktop -> Mouse actions: The action "Vertical scroll" is present, set to "Switch desktop", but the first icon to the right of that (with the left/right arrow symbols) is greyed out.
How many virtual desktops do you have? Does it work if you move the wheel very slowly?
It's configured for 8 desktops, this is unchanged from before the system upgrade. Moving the wheel very slowly doesn't make a difference. One thing I noted, after going back to 20.04 for awhile: that greyed out icon I mentioned is also greyed-out in 20.04 with desktop scrolling working.
Thanks. Looks like this is a duplicate of Bug 419878. *** This bug has been marked as a duplicate of bug 419878 ***