I wrote:
GNOME these days supports user switching ONLY with GDM. :-( (Yet
another
example of how GNOME does not give a darn about interoperability with
anything else.) Even with GDM, it could be broken, but with other display
managers, it is not even expected to work anymore.
PS: Oh, and while for user switching, this has been the case already for a
while, recently, GNOME has started requiring GDM even for SCREEN LOCKING!
(!!!)
Kevin Kofler