Mac Mini 4,1 SPDIF output (Ubuntu 16.04)

I’m running Roon Server on a 2010 Mac Mini (which is running Ubuntu 16.04). Seems to be working fine, so I’ve gotten ambitious. I’d like to use the digital optical out of the Mac Mini to run sound to my Onkyo TX-8050. I’ve been unsuccessful in the past doing so – audio configuration defeated me – but perhaps Roon knows things I don’t? Anyone else done this?

I see an output in the “Devices connected directly to Core” group, which is an “HDA NVidia CS2406 digital”. Is that the SPDIF output? There’s also a similar output that’s “analog”, and three outputs called “HDA NVidia MI 0”. If I enable the digital output, and run a cable from that to one of the Onkyo’s digital inputs, will I have connectivity?

Works! No volume control, but I see that Marcel van der Veldt has an Onkyo extension for Roon which might fix that. Let’s see: I’d need to power the receiver on and switch to that digital input, as well. I’ll have to look at the extension.