I have ordered a Corning optical USB 3.0 cable, 3 meter length from Amazon in the US. I also order 12 pieces of clamp on ferrites from 3 different manufacturers.

These ferrites at 100 Mhz, only have an impedance of several hundred ohms so they may well be limited in their effectiveness of keeping RF out of the DAC. The only way to find ou is to try. There is also a question what is the RF signature of the optical to electric converter inside the female USB socket of the cable

USB 3.Optical? - Optical Cables by Corning

Hope to test in early April

PS cable was US $135 including shipping