HDMI + SPDIF dual audio

It's basically the wrong hardware to do that. An HDMI audio extractor would be the right choice.

Do you use a Kodi app to play music? Maybe there is a chance to switch to S/PDIF over the app.

I used SPDIF for 15 years but am really happy with HDMI audio out of the Pi. In my case, I use HDMI audio from the Pi directly into the receiver.

I couldn't get an extractor to do DD or DTS. My TV won't pass it through, either. The AVR had zero trouble with DD or DTS, including EX and ES, so now I use the second HDMI port for audio and it works perfectly.

There should probably be an FAQ for HT audio out of a Pi. Perhaps some people have audio extractors that handle multi-channel properly and we can start a list?

Assuming the music you listen to is 2 channel, an audio extraction device would work perfectly for you.

It's not possible to get audio on HDMI-0 and HDMI-1 at the same time.

It's also not possible to get audio on HDMI and HiFiBerry at the same time.

-> You need an HDMI audio extractor.

Quote from Draculanium

An audio extractor is not recommended if 4k HDR is required. It does not transmit the HDR signal.

It's just a question of processing speed. No argument against HDMI audio extractors in general. It's difficult to find quality extractors, that's for sure.

Thanks for reporting the result!