University of Louisville published a study in April on how they DON’T work. Not peer-reviewed, but nothing in this realm is.
https://townhall.com/tipsheet/spencerbrown/2021/05/26/new-study-refutes-fauci-efficacy-of-mask-mandates-n2589990
They did not do scientific tests on masks or test the physics.
They analyzed numbers and came to a conclusion.