After removing preinstalled Windows on new Dell Inspiron G3 and installing Ubuntu 18.04 I have run into sound problem. Internal speakers were detected and I could listen to sound, but somehow internal microphone was not detected – similarly laptop didn’t detect inserted headsets mic. After digging quite a lot of time I have found solution to this problem that also have ‘survived’ updating to 20.04 LTS distribution.

First to do is installing alsamixer package through apt-get.
After getting this done I needed to edit /etc/modprobe.d/alsa-base.conf file.
Problem itself was – wrong configuration of sound settings in detail wrong driver for this laptop.

List of drivers is available at https://www.kernel.org/doc/html/latest/sound/hd-audio/models.html .
What I needed to do, was finding proper driver and add it to my alsa-base.conf file.
Also I have found those topics verry helpful:
https://askubuntu.com/questions/1242249/headset-microphone-is-not-working-in-ubuntu-20-04
https://askubuntu.com/questions/1230016/headset-microphone-not-working-on-ubuntu-20-04

# /etc/modprobe.d/alsa-base.conf
# Keep snd-usb-audio from beeing loaded as first soundcard
options snd-usb-audio index=-2
options snd-hda-intel position fix=1
options snd-hda-intel model=dell-headset-multi
options snd-hda-intel dmic_detect=1