Instead of restarting Ubuntu you can restart PulseAudio from terminal:
pulseaudio -k (wait a few seconds) pulseaudio
Disappearing PulseAudio output devices can happen when using Firejail.
https://firejail.wordpress.com/support/known-problems/#pulseaudio
Instead of restarting Ubuntu you can restart PulseAudio from terminal:
pulseaudio -k (wait a few seconds)
pulseaudio
Disappearing PulseAudio output devices can happen when using Firejail.
https:/ /firejail. wordpress. com/support/ known-problems/ #pulseaudio