Alucard_Vampyre
I don't think it's possible to enter the antimatter universe with just magic, like u would need a conduit of sorts something which belonged to the antimatter universe. or if u are as strong as antimoniter than u can just perceive it I guess. But still like magic is called magic for a reason for making impossible possible but in DC it always comes with a price.
The Best way to get in and out Of any verse in DC would be With lucifer helping. he created fhe Dc universe with his brother so he pretty much Can do whatever he wants in It. not even michael Could do so because he Is the Aspect of power of god so he is So powerfull that if he would try to enter an universe it could damage it. but lucifer is the aspect of shaping said power So to him its all about control thus he Is abel to do Whatever he wants in any dc verse. unless the presence it self Stops him.
It's possible to enter the antimatter universe with a lot of ways, is just another universe after all. However, you can't exit the antimatter universe with magic, because magic does not exist in that universe. The anti monitor killed all mages and sorcerers, and eliminated magic from the universe itself, so no magic, except maybe internal magic, but I doubt it as it's a rule imposed to the reality of the universe itself. It's weird. However, its not like creating a portal is hard, the antimatter universe has the Crime Syndicate, and they do have machines to make portals to another universes.