If the Jazz land the #1 pick, it's hard to imagine them trading it away—especially if Cooper Flagg is available. He's the kind of franchise-changing talent you build around. Unless a team offers someone like Jokic or Giannis, I don't see Utah moving that pick. Even then, it would be a tough call.
If they're sitting at #2–4, trading up would be tough. Whoever holds the top pick likely wants Flagg just as badly. It would take a massive offer—probably more than the Jazz should give up at this stage. Better to stay put and grab the best player available.
In short, if Utah gets #1, they keep it. If not, they probably don't have the leverage to move up.