Thank you! That’s exactly a point that I forgot to mention.
Delta-sigma DACs, by design produce prodigious amounts of RF noise. Which is why their output is passed through an analogue low-pass filter, to remove said RF noise. As a bonus, any RF noise introduced upstream of the DAC (i.e., as part of the digital signal chain) will be removed by the same low-pass filter that removes the RF noise produced by the DAC itself.
That’s why the measurements, that I posted links to, showed no hints of RF noise from using a switching power supply (whether upstream for the streamer or for the DAC itself).
If there’s a market for snake-oil, it is the essence of the capitalist system that someone will step forward to supply it.