Hi,
Since the end of the summer I've been enjoying KDE on a desktop computer that is running Arch Linux and most things have been working swimmingly. Wonderful!
There is one thing that I haven't manage to figure out, however: keeping the headphones connected to the front panel and having the computer to switch between playing sound from the headphones and speakers respectively (this only happens when physically disconnecting the headphones, and it happens automaticcaly; then sound will be played from the speakers instead).
Is there any convenient way of accomplishing this? I've tried uninstalling KMix and using plasma-pa instead, and while the latter gives more options and seems to be designed with PulseAudio in mind, it still doesn't work (selecting "Headphones" does indeed make sound play through the headphones but selecting "Line Out" makes no sound be played at all, for the motherboard device in question - "Starship/Matisse HD Audio Controller").

Thank you in advance.
So far KDE and Plasma have been great to me.

Uninstalling KMix is a very bad idea, as it is part of Plasma, and Pulseaudio is the underlying software anyway. You should be able to access all necessary controls in the System Settings, and when playing you can access those through KMix as well.

I thought that both KMix and plasma-pa were volume controllers for KDE, and that one would be enough...? Now I have investigated it further and it was written somewhere that they have slightly different use cases. Upon learning that I reinstalled KMix and nothing bad seems to have happened (plasma-pa is still the volume controller in use).

And I did find a solution to my problem. It was a matter of starting alsamixer, selecting "HD-Audio Generic" and setting "Auto-Mute Mode" from "Enabled" to "Disabled" (at first this was not clear since the bars change in alsamixer when switching between "Headphones" and "Line Out" in plasma-pa).

Now it works as expected and I can enjoy switching between sound playback from the headphones and speakers respectively by selecting "Headphones" / "Line Out" in plasma-pa, without physically having to unplug any hardware. On top of that, it was possible to bind the plasma-pa applet to a hotkey, making it even more convenient. Thank you very much for the help. KDE was not the culprit, and in contrast, now it enables a fast switching between the outputs, just as I a wanted. KDE is neat!