Hi together,
I’m happily using two of those from DeLock.
I was using my RPi4 with an audioquest Dragonfly Red and had mysterious clicking noises coming from my speakers.
The noise came from a Seagate NAS which was connected to the same network switch as the RPi.
I isolated the RPi with one of those and the problem was solved.
They work very well to isolate the LAN Connection completely, including the ground.
I can’t tell if it makes an audible difference in every system, but it’s really cheap and worth a try.