I think it’s best to define “I”. Your sense of self is constructed from the biology of your brain. Your “ego” or the biological and mental character you are observing and observing through is not “I”. Your thoughts, your feelings, sensations etc.

Under all of that, observing everything, is “I”. The only irreducible thing in the universe. “I” am consciousness, the observer that can’t be observed. The only thing that the more you try to grasp, the less it’s possible. But still the more you learn. Because the only thing that IS, is I. Reality emerges from consciousness, not the other way around.