Audio suddenly stops working?

I’ve got a DIY edition running Ubuntu 21.04 and typically connected to a Caldigit TS3 Plus thunderbolt 3 dock. Up until this morning the audio worked fine both docked and undocked. This morning it stopped working altogether-- or almost altogether; when I plug headphones into the headphone jack, I get a buzz and crackle when I do Ubuntu’s speaker test in sound settings, then silence. Testing again gives another buzz and crackle. Nothing through the laptop internal speakers with the headphones disconnected; nothing through the dock’s audio output when docked.

I confirmed that the audio board cable is well seated-- it had come attached with the DIY edition; I tried detaching and reattaching it as per the audio board replacement guide, no change. Repeated reboots and dock/undock connections don’t change the behavior either.

Anyone else had this happen? I’m guessing I most likely need a replacement audio board, but are there other things I might try in Ubuntu to diagnose or fix this?

update: works with the dock after all-- which AIUI has its own audio card-- just not internal headphones or speakers, so it’s much more likely to just be a bad audio board. sigh.