Jason Momoa's Duncan Idaho was a major part of Dune, and while he didn't appear in Dune: Part Two, his role in Dune: Part Three will be much different to what you're expecting. Dune: Part Two expanded the world of Dune significantly by wrapping up the story of Frank Herbert's original sci-fi world, but the recent second film is far from the end of the Dune universe. In fact, Denis Villeneuve has already expressed intereest in adapting Dune: Messiah in live action, with this potential Dune: Part Three making a splash by bringing Duncan Idaho back.

https://screenrant.com/dune-3-movie-jason-momoa-duncan-idaho-return-different/