Who maintains this in eighteen months? If you have an in-house developer comfortable with JavaScript, a React Native or web-first product fits your capacity better than a Swift and Kotlin pair of codebases. If you plan to work with an agency on retainer, the question shifts to whether that agency has depth on the chosen stack.
Codigo, listed among Singapore agencies with both consumer and enterprise work, is described as working on native apps, React Native, UI/UX, and APIs, which is the kind of mixed profile that suits products expected to evolve. The same logic applies to a two-person in-house team: a stack nobody on the team can read is a stack you will pay someone else to touch every time.