I could probably asked, but end user experience would probably be a more accurate reflection. My experience with hdmi was an interesting one, where some equipments does not allow the EARC to turn on with the TV but some does. Hence I tend to look for end user experience as it will be a more accurate answer.
HDMI is a mess of standards, though, while it’s straightforward with Roon Ready / RAAT. I just think that the chance that another forum user has the same (quite unusual) device is rather small. Good luck though.