Check out my recent presentation on ancient Skepticism where I try to get clear on whether, according to Sextus Empiricus, Skeptics had beliefs. I engage with Michael Frede's two seminal papers The Skeptic's Beliefs (1979) and The Skeptic's Two Kinds of Assent and the Question of the Possibility of Knowledge. If the presentation piques your interest, check out the paper here (which is much better than the presentation imo).