I am actually working on a react native app with native modules in objc, swift, and a combination of the two. It is stable and easy to work with all three. Just use what you want to use. You wanna make it full swift, go for it. React native, go for it. Stick with objc you know, go for it. No wrong choice here.

ps: Well, maybe pure objc is not the best choice, since it's on its way out, but it's a long way to its end.