Audio (not including bottom facing speakers) and microphone works with sof-firmware and Linux 5.5 just add the following to /etc/modprobe.d/blacklist.conf
blacklist snd_hda_intel
blacklist snd_soc_skl
Configure PulseAudio's to load Alsa modules with the correct device and channnel settings, by adding these two lines to /etc/pulse/default.pa:
https://wiki.archlinux.org/index.php/Lenovo_Yoga_c940#Linux_5.5_and_later