Some casual googling says “no”, not a true plex client. but plex server provides a DLNA service and I would suspect Dune can tap into that.
Dune has never had a great UI from what I can tell.
I would have been tempted by the hardware had they really made those DACs shine with multi-channel analog out, but alas no.
I’m sticking with my HTPC + JRiver for the main media center room; rest of house is Plex (Apple TV, nVidia Shield), where the rendering devices - video and audio are not on the same level as the media center.