While there is, I believe, solid mathematical and physical evidence for God behind the universe, there is absolutely no such evidence for Satan until humankind abstracts that information from its own mind. It seems an invention to which no form of evil is exclusively of human origin, but is rather attached in some way to this agency.
I’m an OT believer who sees the Serpent as God Himself. Any detachment from this view seems to me to undermine monotheism.
We see Nature constantly reduced to ever simpler terms. Although many of the ways into those terms still seem cloudily elusive, others have oft time been rendered with breathtaking clarity. Such it is, I believe with God, Who made His universe that way too.
They are real and I've met them and no spirit is obliged to respond to your demand for proof.