I also can’t think of any way it could be done that would rule out fakes or delusion. If I saw a being doing things like shift stars to form words, I’d be more inclined to think I was going insane or that we are all in the Matrix than in a God. Both are much more plausible.
Although someone running a simulation with us in it might qualify as a “God” by the OP. Even if he’s just an alien computer programmer.