I had the same problem with Ubuntu 20.04 on my Dell Vostro 5490. Using pulseaudio 1:13.99.1-1ubuntu3.3+lp1881659 from ppa:hui.wang/pulseaudio the problem with no sound in headphones was resolved. When I plug in the headphones, I can hear the sound from them. When I unplug the headphones, sound comes from the speakers. Thank you.
I had the same problem with Ubuntu 20.04 on my Dell Vostro 5490. Using pulseaudio 1:13.99. 1-1ubuntu3. 3+lp1881659 from ppa:hui. wang/pulseaudio the problem with no sound in headphones was resolved. When I plug in the headphones, I can hear the sound from them. When I unplug the headphones, sound comes from the speakers. Thank you.