Thanks, the tip, i forgot about the 'legacy' kernel images. I've booted the most recent build i could find Armbian_21.02.1_Rock64_focal_legacy_4.4.213 and now have audio working.
`aplay -D default:CARD=rki2ssound piano2.wav` will play out of both the onboard 3.5mm headphone jack, and the DAC HAT.
I'm sure i had it working before (2+ years) ago using the mainline kernel. Either things have changed since then, or my memory is faulty.
I see rock64 has more recently moved from CSC -> WIP and there are some new builds. Will try those out and see if things have changed.
