It hasn’t been specifically said, but the History of Sentinel Comics videos specify that a superhero called The Centurion, created by GR Comics, was the first classic superhero in the metaverse, rather than Superman, and that the Wraith was the first hero to do the ‘Batman’ thing, so it’s probably safe to say that there’s no DC.
My assumption is that when History of Sentinel Comics releases, it’ll have a few competitor companies roughly outlined that serve as the primary Distinguished Competition to Sentinel Comics, whereas Marvel and DC won’t exist.