I have been searching through a few forums with respect to 3 x SPDIF output from HD.
The holy grail for me is 3 x SPDIF from a 'box' connected to the HDMI from my Sony Blu-Ray player.

There's some great reviews of the Oppo 981 with such an modification outputting PCM x 3 from SACD and DVD-Audio. An Oppo universal HD DBD, BR, DVD-A and SACD player modd'ed would be something indeed!

System 1:
568.2MM, G98DH, Denon DVD-A1XV, Sony CDP-228ES, UHD722, D5KC, D5500.2K, DSP33, Sony UDP-800, AppleTV 4K, Sony KE85XH9096BU

System 2:
562V, M20, AppleTV

System 3
501, 555, AppleTV, Acoustic Energy AE1