Roon bridge + NUC + No dedicated DAC = purple signal path?

Running some flavour of Linux on one of the recent 7th gen (Kaby Lake) NUCs and Roon Bridge, via HDMI to a receiver - is it possible to get the purple light signal path, or is it stuck on OS Mixer/Green (like my laptop) without a dedicated usb DAC?

I think I can answer this myself - if you set the endpoint up with exclusive mode the signal path goes purple (on windows anyway). I gather this is cause system sounds/other software can’t use the audio device at the same time.