Hi @daltonlin I also have an HP Chromebook 11 (G6) which has a sound problem. The internal speakers and mic only show “Dummy Output … Input”. However, I can get input and output by using Bluetooth devices.
Did you ever figure out a solution here?
Welcome to 
I am moving your post to a new topic. The original here was more that 3 1/2 years old. Closing the old thread.
As a new topic it may get the attention it deserves.
On a previous distro I downloaded soffirmware
Rebooted and it worked perfectly on my Lenovo Chromebook!