Just to make a test, I attempted to remove Gnome D.E. from my 11.1, using Yast and selecting patterns.
With my surprise the only permitted operation are “install or upgrade”; I am not able to select uninstall/remove.
My scope is to uninstall all Gnome D.E. and then install it again, to see if this solves a problem on my laptop sensitive audio controls, which stopped to work when I use Gnome, but that work perfectly when I am on KDE3.5.
(Beside Gnome, I have KDE4.1 and KDE3.5 on my box).
You can do this:
With the filter on Patterns, in the LHS highlight Gnome DE. Then in the RHS do right click on any installed application and select “all in this list” → delete. Wait a while for the dependency errors and select your options to solve them. Then click “try again”. Then proceed.
It’s not without danger to your installation – be careful.