I recently installed ubuntu 20.04. on my Acer Swift SF314-57. Ubuntu does not recognize my built in microphone. The microphone works just fine in Windows 10.
I had problems with the sound card after ubuntu installation as ubuntu did not show it and respectively only dummy output in my sound output options. I fixed this by editing /etc/modprobe.d/alsa-base.conf adding options snd-hda-intel dmic_detect=0. The sound output works fine now. If I connect a headset, sound and microphone both work. However, the built in microphone is not detected.
So far I tried editing /etc/modprobe.d/alsa-base.conf and adding either options snd-hda-intel model=dell-vostro enable=1 index=0 or alias snd-card-0 snd-hda-intel & options snd-hda-intel model=auto or all three of them.