Lets jump straight to Yisro, because that’s what its all about.
There is no scientific evidence which can prove that matan torah didn't happen. Lucky break there ! Archeological evidence deems it unlikely that millions of people fled Egypt and camped in the desert for 40 years with no evidence. However we all know they ate mon, so there were no empty plastic bottles or McDonalds boxes for the archeologists to find.
Seriously though, the numbers by matan torah could be exaggerated, in those days certain numbers were 'idealized' e.g. the number 6. In our days it’s 42. So its quite possible that many thousands of people left Mitzrayim, had a revelation at Sinai, and there would be no scientific or archeological evidence to disprove this.
As to what the revelation actually consisted of, now that's a whole different question.