Ok, I’ve confirmed that KANN Cube requires a Windows 10 PC or Mac (running Roon Bridge) to receive USB audio running in DAC mode. The PC requires the KANN Cube USB port driver to be installed (supplied with the KC). I recently acquired an inexpensive Intel NUC that I’ve been using for this, it acts as a Roon endpoint to bridge my KC DAC to my Roon Core PC via an ethernet network.
This issue is resolved.