No sound after upgrade to 18.10, only a dummy device is shown

Try

sudo apt purge timidity-daemon 

and

reboot

I turned out that the cause where old pulseaudio config files. I did remove them with:

sudo apt purge alsa-base pulseaudio

This will cause some dependencies to be purged as well. So the easiest way to reinstall everything is to do:

sudo apt install ubuntu-gnome-desktop

But this might bring you some packages back, you had intentionally removed before. So keep track of what is being installed.

Another way to reinstall what was removed is to simply copy the list of uninstalled packages from the terminal:

The following packages will be REMOVED:
   alsa-base* indicator-sound* libcanberra-pulse* paprefs* pulseaudio* 
   pulseaudio-equalizer* pulseaudio-esound-compat* pulseaudio-module-bluetooth* 
   pulseaudio-module-gsettings* pulseaudio-module-raop*
   pulseaudio-module-zeroconf* ubuntu-desktop* ubuntu-gnome-desktop*

So for me this was:

sudo apt install alsa-base indicator-sound libcanberra-pulse paprefs\
pulseaudio pulseaudio-equalizer pulseaudio-esound-compat\
pulseaudio-module-bluetooth pulseaudio-module-gsettings\
pulseaudio-module-raop pulseaudio-module-zeroconf ubuntu-desktop\
ubuntu-gnome-desktop

After you have reinstalled everything you shout do:

sudo alsa force-reload

After this the sound device should work again.