This question, when answered beyond all doubt, leaves the seeker ... well. BEREFT. Bereft of any and all concepts, bereft of "identity" or and so called real and solid "beingness", bereft of nothing, everything, etc ad nauseous! Bereft thou shall BE in nowhereness, where (where?) nothing Happened never did never will... Absoluteness, bereft of any and all of the usual "nondual spiritual 'pat answers'", i.e. when the question is answered with nothing by nothibg for no one, there is That which has never changed never has never will. full stop.
You are not That and You are That. Or, as succinctly phrased by John Greven, a man who exists only in an appearance of an ocean wave-ing (and saying "hello waves"):
"From nothing comes something and to nothing the something returns. But having never left, there is no returning, for something into nothing. In the end nothing happened in something and something never happened in nothing".
Never Changing, therefore unknowable by "you and me", yet ... That IS.
Questions? Comments? Arguments? OK, write firstname.lastname@example.org. Sincere questions are most welcome. But don't bother with agreeing. Look into it and have fun.