The 2017 apple iMac is one of the last Intel iMacs produced but unfortunately it is fitted with a Cirrus Logic CS8409 audio codec. Stock Linux sees the Intel audio controller but not this codec. There are some branches in Github that get it working but these have not been committed in a repo so every time I run software update the sound stops working.
There must be thousands of affected machines from this batch all affected with the same problem. Is there anyway someone can push out a permanent fix for this?
Have you tried it with the script from the github link shown here? There is mentioned a dkms module, so you shouldn't get problems after kernel updates. But I'm not sure, I have no Mac.