How can I use an inductor as an EMI sensor?
You can see one design from the Elektroscluch [0]. It seems to be as simple as connecting an inductor to ground and then feeding the &quot;positive&quot; end into an amplifier (and in your case an ADC). I don't see why you need two inductors here. This circuit uses one.
Given the sampling rate of 500kHz (if you copy the paper), you might want to put in a low pass filter around 200-250kHz anyway. On the PCB in the supersensor papre it looks like there may be an RC filter just off to the right, which maybe feeds into an op-amp buffer (unity gain amp) U8. That's a guess though, since there's no schematic.
Their conference paper does cite a couple of references that may be useful, but they seem to be more related to power line monitoring, not inductive/contactless. For example:
https://ubicomplab.cs.washington.edu/publications/electrisense/
https://ubicomplab.cs.washington.edu/publications/lightwave/
Both these papers show that lots of interesting emission in the low 100s of kHz which matches with the sampling rate in the paper.

[0] https://github.com/LOM-instruments/Elektrosluch-3-plus/blob/master/hardware/elektrosluch_schematic.pdf
Another example they cite is the Syntonistor project from CMU - that seems closer, although a lot of the conditioning circuitry here doesn't seem to be on the Synthetic sensor PCB (but who knows, we only have a photo of the top side). Also it's designed to detect 60Hz, but you could tap off the signal just after the inductor.
https://www.andrew.cmu.edu/user/agr/projects/syntonistor/