The Dune Encyclopedia strongly implies that sandworm flesh is inedible and almost certainly poisonous.
The resulting electrons passed to an electron acceptor believed to be a cupri-cyanide compound, the reduced form of which accumulated in the worm body.
Our knowledge of the metabolism of the sandworm is necessarily
incomplete, not only because of the size of the creature, but also
because of the presence of many acidic compounds in the worm body.
Besides the organic acids, concentrated hydrochloric and sulfuric
acids have also been detected. In some way the living worm buffered
itself against these acids, but once the worm died, the body was
rapidly digested by them.
While eating something that contains poisons isn't necessarily impossible, it's hard to imagine what processes you could use to remove cyanide and highly corrosive and toxic acids from the meat before eating it.