Does Dragonboard410 C has analog pins (for audio)?
Looking at the document you linked, you can find this information on section 7 Analog Expansion Connector.
Hope it is what you are looking for.
Of course the 410c has analog Audio inputs and outputs. There is an app note on using the connector https://developer.qualcomm.com/download/db410c/stereo-connector-and-audio-routing-application-note.pdf. I have updated the app note to fix one error, and to make everything a little clearer. I have completed all the document updates, but the updates are not yet posted. I hope they will get posted this week.
Full Disclosure: I am an employee of Qualcomm Canada, any opinions expressed in this or any other post may not reflect the opinions of my employer.