Linux kernel does not recognize Topping DACs' ability to play native DSD, as Thesycon's vendor id is not listed in the kernel.
I submitted a patch to solve that issue
https://git.kernel.org/pub/scm/linu.../?id=1ea0358ecb848058b35b6da13d7f4c08610a73a8
The code will probably ship with the next stable version kernel. But in the meantime, if you need to use Topping's DAC to play native DSD under Linux using MPD, you need to patch in this line and recompile your kernel.
I submitted a patch to solve that issue
https://git.kernel.org/pub/scm/linu.../?id=1ea0358ecb848058b35b6da13d7f4c08610a73a8
The code will probably ship with the next stable version kernel. But in the meantime, if you need to use Topping's DAC to play native DSD under Linux using MPD, you need to patch in this line and recompile your kernel.