In order to replace the default Xubuntu deamon notifications with dunst, you have to, once dunst compiled and installed, disable the dbus service file :

sudo mv /usr/share/dbus-1/services/org.xfce.xfce4-notifyd.Notifications.service /usr/share/dbus-1/services/org.xfce.xfce4-notifyd.Notifications.service.disabled

You must then check that the /usr/share/dbus-1/services/dunst.service file exists, or create it if necessary

sudo vim /usr/share/dbus-1/services/dunst.service

The content of the file will be as follows:

[D-BUS Service]
Name=org.freedesktop.Notifications
Exec=/usr/bin/dunst

It works because Dunst is started automatically via a dbus service usually located in:

/usr/share/dbus-1/services/

However, this does not seem to be the best of techniques, because from a ‘Linuxian’ point of view, manually change files in ‘/ usr’ are never well regarded.                                                                                                                          I would update this article if I find a more elegant solution.