I have an very inexpensive ART pre amp and I plugged the mic into that, then went into the line in and no hum at all.
Just annoys me that several people have this problem, it should never arise in the first place, other modules don’t do it.
They really bigged up the pre amps on this unit but what’s the point if you can’t apply a decent amount of gain? I tried recording a finger picked guitar part and it was unusable.