See this bug report and see if it helps 206589 – No way of getting sound with the ALC294 from the Asus Zenbook (Flip) Series
Are you dual booting with Windows? Disable fast boot from it.
Other Asus models with the same Audio card seem to have some solutions
https://bbs.archlinux.org/viewtopic.php?id=255468
https://bbs.archlinux.org/viewtopic.php?id=235291
https://bbs.archlinux.org/viewtopic.php?id=249456