Does Superman have a post-credit scene?

Two, and neither of them is homework. James Gunn splits them across the crawl: the first arrives mid-credits, once the principal cast cards have gone by, and the second waits until the very end.

The mid-credits scene runs about thirty seconds and contains no dialogue. Superman sits on a lunar ridge with Krypto in his lap and the two of them watch the Earth turn — weather systems, city lights, the whole slow rotation — while Krypto does very little except be a dog. It plays as a breath rather than a beat, and it quietly restates the film's central argument: he does not belong to Metropolis, he belongs to all of it.

The post-credits scene is a joke at the hero's expense. Back in the rebuilt city, Superman and Mister Terrific stand looking up at a skyscraper Terrific reassembled after Lex's dimensional tear ripped the place open — and it is very slightly, unmistakably crooked. Clark points this out. Terrific, who has spent the entire film being the most competent person in any room, declines to take the note and walks off without a word, leaving Superman muttering "I shouldn't have brought it up… gosh, I can be such a jerk."

Neither scene sets up an announced project, which is a strange choice for a franchise-launching film and a deliberate one. Gunn has said on the record that his time at Marvel taught him not to plant stingers for things that may never pay off, and he would rather promise nothing than promise wrong. The genuine handoff to the wider DCU happens inside the film instead, in the last scene before the credits, when Supergirl turns up at the Fortress to collect her dog.