I just installed the X-USB and can confirm that it works on 48 kHz (and 44.1 kHz) just fine (been running for about 2h straight now).
The noise on the uTrack was present on all 16 local channels. As you can hear near the end of my sample recording, the noise isn’t constant but “follows” the actual signal’s amplitude. I’m not sure whether or not it was present on the channels coming from my SD-8 on AES50-A. Gonna check this next now.