I'm running Kubuntu 18.04. In Xenia 20.04, it seems that you need the modules indicator-sound and indicator-sound-gtk2 to get the volume control on the taskbar. But that doesn't work in 18.04. So what do I need?
I think the problem lies in some configuration file, since when I created new user, that user did have the sound indicator.
You can try this:
sudo apt-get install indicator-sound
killall unity-panel-service
killall gnome-panel
or
sudo apt-get install indicator-sound
sudo apt-get install indicator-messages
sudo apt-get install evolution-indicator
Hope this helps.
You can even try this, it worked for me.*
sudo apt-get purge pulseaudio
sudo apt-get clean && sudo apt-get autoremove
Reboot. Open a terminal again and type (ignore any errors with the rm command):
rm -r ~/.pulse ~/.asound* ~/.pulse-cookie ~/.config/pulse
sudo apt-get install pulseaudio
Note: if you get E: Unable to correct problems, you have held broken packages. error, then you can try:
sudo aptitude install pulseaudio
(if you don't have aptitude on your machine: sudo apt-get install aptitude)
sudo alsa force-reload
pavucontrol
The last command should restart the PulseAudio server and launch a desktop application for its settings.
*Note: Using apt instead of apt-get may work as well.
Reference = https://askubuntu.com/a/435221/1013762
Hope this helps.
Hooray -- I got my loudspeaker icon back. The trick was installing kubuntu-desktop. Seeing that work explained why none of the other suggested solutions worked. I had been climbing the wrong mountain.