IIRC has Synology disabled USB Audio support in DSM 7.
As I understand it, this is an oversampling DAC-Chip. 768 kHz is the frequency after the filter but as the clock is there it gets supported on the input too – but half the data just gets ignored because the filter input is 384 kHz max that then gets oversampled and filtered (to 768 kHz before further processing). 768 kHz is also listed as max USB output frequency. I assume they use a Linux of some sorts as OS – so specific DAC drivers may be harder to come by as with Windows. While there might be a slight chance for a given DAC to be supported, most probably won’t. Currently most DAC’s supporting 768 kHz are in the same boat regarding supported sampling frequency as the DMP-A6 (oversampling DAC-Chips that allow for 384 kHz max as filter input). So it seems to me that there is currently hardly a need to provide 768 kHz support. But again, you need to discuss this with Eversolo – Roon can do higher sampling rates when signaled as supported by endpoints. If the Gen 2 differs from the OG device then its firmware must reflect that and the device may even have to undergo the certification process again.
PS: Roon Labs staff doesn’t monitor threads in Audio Gear Talk. There are just other users discussing here.