headphones, no sound from onboard card

[Mac]

I have a GA-Z77X-UD5H (rev. 1.0) that I recently installed Ubuntu 21.10

The Gigabyte website says that the motherboard sound controller supports the Realtek ALC898 codec.

I created an Alsa report; see link below:

http://alsa-project.org/db/?f=43a1cb48648835a145be78f7bf474d1507d69124

Although I can't get the sound working through the headphone using the jacks at the back of the computer, the sound does work via the GPU and monitor. The headphones function as expected under Windows 10.

alsa-base is (1.0.25+dfsg-0ubuntu7).