Other than (metaphysical) anti-realism, which I’m under the impression is an umbrella for all types of denial that there is an independent, external reality.
I suppose you could even envision someone taking the stance that there is an external reality, because they have found empirical proof, which would make them a realist as well as a proponent of whatever this is.
could be Phenomenology; we only know what we sense - but we cannot know if what we sense is accurate or complete; in fact it is neither. We have no way to truly “know” the nature of reality or if it is independent of our own existence. By “we” I of course mean ME, because I only sense your presence tangentially - only MY existence is certain (to me).