Fabulous

Fabulous lets you build cross-platform mobile apps using F# with a functional programming approach. If you're an F# developer (or want to be) and need to ship iOS and Android apps, this is your path. It sits on top of .NET MAUI and gives you a declarative, Elm-style architecture.

The pitch: instead of the imperative, state-mutating approach of most mobile frameworks, you describe your UI as a function of your state. State changes, UI re-renders. If you've used React or Elm, the mental model is the same. Small community but dedicated. F# is a niche language and Fabulous serves that niche well.

Completely free under Apache-2.0. No paid tier, no cloud service. You need a .NET development environment and the platform SDKs (Xcode for iOS, Android SDK).

The catch: F# is niche. Finding F# mobile developers is hard. The ecosystem is small. Fewer libraries, fewer Stack Overflow answers, fewer tutorials compared to React Native, Flutter, or even Kotlin Multiplatform. If you're not already committed to F# and .NET, there's little reason to choose this over more popular options. But if you ARE an F# shop, this is the only real option and it's good at what it does.