I recently purchased a Flatmax Pro v2.15 through Amazon. I found the audio-injector github repositories, but there isn't one for this card.  I looked in /boot/overlays and picked the overlay for the "isolated" card and added this to the /boot/config.txt:

dtoverlay=audioinjector-isolated-soundcard

and commented out the dtparam=audio=on line. The adapter now works. Is there a better configuration to use?  I updated to the latest available code (kernel 5.10.63-v7l+).

I find the adapter doesn't hear some of the audio devices I have, whereas a SoundBlaster X-Fi does hear them (I intended to replace the X-Fi with this board).

What's in the audioinjector-addons overlay?

Thanks,

Glen Overby