The information that you provide is a bit too sparse to enable us to suggest what is going on. So perhaps you will kindly give some further details.
Exactly what are your problems?
What streaming service are you using?
How is the Vivaldi upsampler configured? Are you upsampling to a higher resolution or are you trying to play native high-res files from the streaming service?
How is the upsampler connected to the Vivaldi DAC?
I am unsure what yu mean . To play files requires playing software, you cannot play by USB on its own. Do you mean using the Melco playing app connected by USB? Is USB 2 selected ?
Perhaps you could explain. I have no idea what the SOTM device is ( they make several) nor what a linear font is.
I have no guarantees that I may have an answer to suggest but this additional information will allow me to think further.