OK I'm kinda stuck trying to get 4.1 to produce sound, so I've decided to try applying the 4.0.9 patches to the 4.4.x source code. Will see how I go....
4.4.238 code is compiling - with a bunch of warnings (some of which will need to be actioned) - and 124 missing symbols - down from 150+ this morning 
Down to 5 missing symbols...
OK I got it to link - the final missing symbol was a hack, but it will do for now.
Current status is that AC97 hardware boots (at least my virtualbox system does), but HDA traps (on virtualbox).
I'm currently investigating the HDA traps, but if anyone has AC97 hardware and wants to help confirm the core at least works, feel free to try
http://smedley.id.au/tmp/uniaud32-linux-4.4.238-20201018.zipAgain: this code traps on Virtualbox with HDA hardware and a Sigmatel mixer.
Cheers,
Paul