Apparently, this isn't actually Superman 2, as reported on SuperHeroHype:
On one of his posts on Threads, where Gunn stated that he was busy with sequel writing, a user named @alexromval asked, “I’m a little confused right now. Is this the same movie you’ve talked about in the past, the one where you said Superman had a major role but wasn’t exactly a sequel? Or is this a different movie, and this one is actually ‘SUPERMAN 2’?”
To this, the veteran filmmaker replied, “Yes, yes, sorry. This is the same movie. Superman has a major role. It’s not Superman 2.” Another user asked Gunn if this movie is “not a direct sequel to Superman?” In response, he conveyed that Peacemaker Season 2 is more of a direct sequel to Superman, featuring David Corenswet.