I have been a gnome user for I don't know how many years. Now that gnome is getting dull (sorry) I have decided to give KDE a (new) chance. And I love it.
I have one (till now) problem though : synaptic (I use Debian) gets its root privileges when started from gui as SU. Now, I have the root account disabled so I don't use SU to give an app root privileges, but sudo. In gnome I had gksu and gksudo. Synaptics use gksu equivalent (I couldn't find it's name, I thought it is kdesu but it's not) and I installed kdesudo.

For gksu I had an option to make it use the sudo command, not su, for root. How do I do the same for the kde-su app (I still don't know how its called) or make synaptic use kdesudo. Thanks.

from the Arch wiki (and a mighty fine Wiki it is) https://wiki.archlinux.org/index.php/sudo

kdesu

kdesu may be used under KDE to launch GUI applications with root privileges. It is possible that by default kdesu will try to use su even if the root account is disabled. Fortunately one can tell kdesu to use sudo instead of su. Create/edit the file ~/.kde4/share/config/kdesurc:
[super-user-command]
super-user-command=sudo

if that doesn't work you may also need to do

PolicyKit

When disabling the root account, it is necessary to change the PolicyKit configuration for local authorization to reflect that. The default is to ask for the root password, so that must be changed. With polkit-1, this can be achieved by editing /etc/polkit-1/localauthority.conf.d/50-localauthority.conf so that
AdminIdentities=unix-user:0 is
replaced with something else, depending on the system configuration. It can be a list of users and groups, for example:
AdminIdentities=unix-group:wheel

or
AdminIdentities=unix-user:me;unixuser:mom;unix-group:wheel

For more information, see man pklocalauthority.