With VOX I got my 818v3 USB input to recognize MQA. Under Audio settings I have these two boxes checked (first one is likely key):

Synchronize Sample Rate with Player
Obtain Exclusive Access (Hog Mode)

Should work with Explorer 2 as well.

Soundserge

Antipodes CX + Roon, 818v3, DSP 7200SEs, 218, DSP3200s