one truly irritating thing about the motu interfaces is that the computer mains out does not appear as an input to the mixer…Therefore its not easy to re-use this signal for other mixes/outputs…
HOWEVER, if you cable up spdif out>spdif in and set your computer audio default to spdif out, then you can assign spdif in (computer audio) to multiple buses.
of course if you have an 828mkIII you can use toslink for this instead.
regards,