Yeah, Legendary Picture announced almost four years ago that they’d acquired both the film and streaming rights to the Dune franchise.
A lot of people keep referencing Warner Bros as if they’re the studio financing the movie, but they’re technically just the distributor.
That said, Legendary appear to have made a distribution deal with Warner Media over Dune, at least in the short term. WB is distributing this first film and probably at least the next one after (should it get made) and a streaming series called The Sisterhood is in development for HBO Max.