May be it is time for me to visit a ear-test.
I can't hear that hum.
The strumming guitar is recorded precisely, the KM184 are my favorite alrounder mics.

"Hum" doesn't seem to be the right word - perhaps "hiss" would communicate what you mean more precisely, if I may make the suggestion.

Playing back your recording, it seems as though the mic pre-amp level on the UCX was set pretty high, as the performance peaks at -2.4 dBFS. Any pre-amp will get hissy when it's set at its higher levels, even those in the UCX.

How are you monitoring? Headphones? Every imperfection is far more noticeable over headphones - hiss, finger noises, metronome bleed... How objectionable is the hiss when you play it back over speakers at a comfortable listening level? Playing it back here over my speakers, the hiss isn't particularly noticeable, let alone excessive.

What I do notice, however, is the very close microphone placement. Try a mic position that is 10 or 20 cm. further away and see if you like the results. There's nothing like a little distance to make finger-noises, body shifts and other human sounds become much less of an issue, and can also make the performer feel like they're a little less "under the microscope", if you know what I mean. And don't aim to get the loudest possible recording - peaking anywhere between -10 and -20 dBFS is perfectly acceptable, especially if you're making 24 bit recordings. And I bet the hiss will be much less of an issue.