Comment 9 for bug 1684108

This bug is caused by module-device-manager not being loaded when pulseaudio starts. This command fixes the issue and restores pulseaudio KDE integration:

$ pactl load-module module-device-manager "do_routing=1"

This command is included in the pulseaudio startup script for X11, /usr/bin/start-pulseaudio-x11, which is included as part of the XDG autostart scripts via a reference in /etc/xdg/autostart/pulseaudio.desktop. As far as I understand the FreeDesktop standard, .desktop files in the /etc/xdg/autostart folder should be executed by the desktop manager on startup, which in the case of KDE is controlled by the script located at /usr/bin/startkde, but the version shipped by Kubuntu does not seem to make any reference to /etc/xdg/autostart files.

I have tested that /usr/bin/start-pulseaudio-x11 is not being ran on startup. I have no idea how KDE is starting pulseaudio, and since pulseaudio is part of the poetteringverse, determining its execution model or startup sequence is beyond the comprehension of mere mortals; but lack of integration between pulseaudio and phonon (the audio system settings module) is due to that module not being loaded, due to that script not being ran, due to, I assume, KDE not executing XDG autostart desktop files.