Here is what I asked: is it accepted within the community that it's an indisputable fact that "there is nothing other than atoms and void", or is it thought to be a belief that may or may not be true or provable?
I would say it is accepted as fact that it is true that we live in a purely material universe. "Atoms and void" is the shorthand for this foundational tenet of the philosophy. From my perspective, it's no more a "belief" than to say that someone hasa "belief" in biological evolution or a "belief" in gravity.