I too have downmix as needed selected. This has no effect because nothing is ever downmixed. The Roon folks have said that if two-channel music is played using a 5.1 or 7.1 HDMI output the results is that 5.1 or 7.1 is sent out but all but two channels are silent. My Anthem processor and my Denon receiver interpret this as a multichannel signal and won’t apply upmixing meant for two-channel sources, including Anthem Music and Dolby ProLogic IIx.