A bit off-topic, but what's the best method to build cross-platform mobile & web apps nowadays ? I'm talking either business logic + UI , or just business logic ? like gomobile, rust, typescript, etc ? At some point i thought about using typescript for all business logic, as it seemed the most portable tech, but i realized there's no good way to have decent performance running javascript on iOS.
My team achieved better than native performance using RN when rewriting a very large iOS app. And that was in 2018, before Hermes and a lot of other optimizations. It takes some careful usage of requestIdleCallback and avoiding doing work in the UI thread but it is not rocket science. You do have to avoid a lot of the going advice and bloated libraries / frameworks though.
You had an app written natively in Objective-C or Swift, switched to single-threaded javascript React Native, and then your app ran faster?