I use Intona between the streamer (LHY RPI Pro) and DAC (T+A DAC200). It makes a worthwile improvement in sound quality. I also own a few isolators with TI ISOUSB211 chip, which work nice. Small differences between them. HQPlayer’s Jussi Laako has shown some measurable improvements USB isolators (Intona 7054-X in this case) can bring, like removing USB packet noise. But USB isolators don’t have an effect on Diretta, it still sounds different compared to let’s say, HQP’s own NAA.
EDIT: Let’s add: IMO and in my setup with my ears etc.