I have sound issue in 18.04. I was installed 18.04 four months before, at that time no issue with sound, but yesterday i was connect to HDMI projector, after that the system speaker or external speaker having no sound when the player is working. Solution please
I had this issue after not installing third party software and update in the first installation step in Ubuntu 20.04 LTS. You should just shift from gdm3 to lightdm to resolve this issue by opening the terminal and typing:
sudo apt-get install lightdm sudo dpkg-reconfigure lightdm
After entering these commands if you are asked that only one of gdm3 or lightdm ubuntu can use then simply select lightdm when asked. This worked for me.
The problem could be that the sound driver is not installed. You'll need to check with your manufacturer about what sound card is in your device to find the correct driver, but you can try with the Intel Sound Driver (which is a common one) by running
sudo apt install firmware-intel-sound
You could also try enabling the Pulseaudio sound service if it is disabled by running
pulseaudio --start --log-target=syslog
(If it is disabled by default, you'll have to re-enter it every time the system reboots (or add it to the startup services with the "Startup Applications" program)). The Pulseaudio volume control program lets you manage the sound with a graphical frontend.
Install it with
sudo apt install pavucontrol
You can try re-installing the core sound packages with
sudo apt install --reinstall alsa-base alsa-utils pulseaudio linux-sound-base libasound2
If all of that fails, try killing the service with
killall pulseaudio; rm -r ~/.config/pulse/*, followed by a reboot.