iphone 15 compatibility with DSD playback via DAC

I successfully connected my FIIO Q3-MQA to my iphone 12 Pro using an OTG lightning to USB-C cable. It passed hi res PCM and DSD (via DoP).

Now I have the iphone 15 Pro Max. PCM is passing but not DSD. It is being converted to PCM as far as I can tell. I have tried all kinds of cables including the vendor's USB-C to USB-C OTG cable and am getting nowhere.

Any thoughts? Hopefully this is something that just needs a firmware update for the phone or DAC.