Seeking advice on mentoring without participating in exam cheating in the new chaotic environment of the pandemic
If I were to try some online sleuthing, the first question I would ask is for the course's website, if there is one, or for links to recent assignments. This has the double benefit that your primary goal in doing this is to make sure that your instruction is as helpful as it can be.

If students cannot provide this, then my next question would be about how you can go about contacting the teacher, for the same reason.  Your instruction can simply be better targeted at this point if you have some sense of what the course is doing.

My guess is that at this point, most cheaters who wish to hide what they are doing will give up on working with you.

(As an aside, you may find that some teachers have, as a practical matter, made their exams entirely open-internet and open-help, and hold a standard that if the student understands what they have written, then they will accept the work. In this case, your assistance might not be considered cheating at all.)