Alternatively, SCADE which write in Swift and run native app in iOS and Android. They are partner with Perfect web framework team that are developing Server-side Swift.

We think it will be more performant with Swift 4 release soon this year. The benefits for using Swift over RN is first-class support and optimized with LLVM and Clang.

Useful for intensive processing, gaming and AI that RN is not a suitable choice. Likewise, LinkedIn iOS app is written in Swift.

http://scade.io or chat with the team at http://perfect.ly