If you mean mouse wheel scrolling on an open spot on the desktop, check whether that’s enabled. Right-click the desktop and choose “Configure Desktop and Wallpaper”, and then click on “Mouse Actions”. If the action of scrolling over the desktop is not listed there, then you can easily add it.
Other than that, you can also use the scroll wheel over the desktop pager in the panel.
I have the same problem.
Its still broken.
Thanks for posting workaround & link to KDE bug report. Workaround does the trick.
BTW running kubuntu 20.04. No problem.