T+A reply to my query:
“The DAC8 DSD currently supports only Windows and MAC OS operating systems. On Linux, DSD playback usually only works up to DSD128. The DAC 8 DSD was never advertised “compatible” with Linux. In the long term, however, the adaptation to the Linux Kernal is also planned. This requires a software update of the Amanero chipset, which would then have to be carried out at the factory.”
Doesn’t look as though anything has moved on unfortunately.