Ok I made some progress.
I used the latest Bullseye Image for the BBB (kernel 5.10.168-ti-r72) as a base.
Then patched (https://github.com/anbraten/beagle-bone-builder/tree/master/resources/ctag-2.4) and compiled the drivers for snd-soc-ad193x, snd-soc-ad193x-spi and snd-soc-davinci-ctag-face-2-4, copied them over and confirmed that they load.
Then I updated the uEnv.txt (see uEnv.txt of my last post)
Now I can play sounds on 2 channels, but not on the other 6.
If I try recording something it also doesn't "really" work. Sometimes I get a very noisy file, sometimes nothing.
Did anyone get as far as to record something successfully? Or did you just test by playing back a test wav file?
@giuliomoro if I try to use your device tree branch then the image won't even boot anymore.