Looks like Roon believes it doesn’t support DSD or multichannel as it’s downsampling to pcm and also mixing down to stereo. Your processing speed on the nuc is pretty low at 2x to this may be a factor of it drops too low to overall performance.
Are you 100% sure you actually activated the HDMi output from the Nuc in settings audio as the zone to play to and this is what’s being used and not the Roon Ready input which is limited to 2.0.
As this looks very similar problem to this users.
What is the DSD strategy set to as well? I think it’s not on DoP which may also be an issue if it is the HDMi output.
Looking at lyngdorfs site it doesn’t mention DSD at all in the Mp50 specs. So the conversion to pcm seems to be right but the downmix maybe a configuration issue. I imagine your dune player is converting to pcm internally and sending multichannel PCM to the Lyngdorf not DSD.
Dolby Digital EX, Dolby Digital Plus, Dolby TrueHD, DTS, DTS ES Discrete 6.1, DTS ES Matrix 6.1, DTS 96/24, DTS-HD High Resolution Audio, DTS-HD Master Audio, DTS:X, AURO-3D®
Post processing: Dolby surround, AURO-MATIC®, Auro 2D, DTS NEO:X, DTS Neural:X, movie, game, music, stereo, party
Audio inputs: 8 x HDMI (≤192kHz/24bit), 1 x AES/EBU S/P-DIF input (≤192kHz/24bit), 3 x S/P-DIF coaxial inputs (≤192kHz/24bit). 4 x S/P-DIF optical inputs (≤96Hz/24bit), 1x USB audio input (≤192kHz/32bit) , 1x XLR mic. input for calibration