I2S audio (with Mopidy) in paralell with HDMI (Kodi)

I have an RPI3 with OSMC installed. It is connected to the TV with HDMI.
I also have a PiFi DAC (HifiBerry clone), connected via I2S.

The DAC works fine, after some hacking I managed to get audio from it with selecting the proper output in Kodi.
I would like to setup a system, which can:

  • play movies in Kodi (audio output to HDMI)
  • simultaneously play music via Mopidy to though the I2S DAC to my stereo (located in a different room)

I’ve never used mopidy, neither a separate DAC, nor I configured linux audio so I figured it was going to be a deep dive…

I did some googling in this topic, and initially the idea I got was to install Mopidy-alsa and use ALSA mixer for the mopidy-I2S audio, and Kodi will manage its own output. I managed to install mopidy and the alsa extension, however I bumped to several errors. At this point IMHO the exact configs and logs are irrelevant, I figured i’m really blind on this. I’m not even sure using ALSA is the way to achieve my goal. I guess I need some advice.

The least I would like to achieve is using the two interfaces after on another (not simultanously) without changing any settings in Kodi or Mopidy.

Actually, I would gladly take any help or hints what to try on this. For a start, it would be nice to configure mopidy to recognise my DAC properly.