Internal microphone doesn't work with Realtek ALC268 chipset
I have this problem with Ubuntu 18.04, 18.10 and Linux Mint 19, on a HP Pavilion dv6700 and a Acer Extensa 5620Z, with a Realtek ALC268 chipset.
Audio is working but not internal and external microphones.
I reported this bug on https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1809093 and on https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1810560
Duplicated bugs can be found on https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1591535