that this symlink is actually always created by the postinst script of
the display manager (on Debian, Fedora uses the [Install] section of
the .service file for that by setting an alias to
display-manager.service) and looking at the source code of the kdm
Debian package, this particular part is actually missing in the kdm
package while it is present in the lightdm package. So it's actually a
bit surprising that the link was installed on my test system.
[...]
It actually depends on which package you reconfigure. So, if you run
"dpkg-reconfigure lightdm" (provided that lightdm is installed) and
choose "kdm as your default DM, it should work. However, if you do
that with "dpkg-reconfigure kdm" and choose "kdm" or any other DM for
that matter, it shouldn't work.