> What is the size of a minimal Fabulous app?

Agree this is interesting. Historically, Mono-applications on mobile was at least 10x bigger than Java application as they included the entire runtime system.

Can the runtime system be shared now? Is .NET Core a thing on mobile, and is the resulting download smaller?

While download size is no longer a problem for me, my guess is it is still a big problem many places in the world.

Mono is still used on mobile, but a unification will occur in the future when .Net Framework is sunset and all there is is .Net 5. .Net will target Windows, Linux, macOS, iOS, Android, tvOS, watchOS and WebAssembly ++

If you enable linking, stripping away unused code, the overhead on Android is minimum 2.9MB compared to your app itself.

Thus a minimum app is perhaps around 10-11MB, but in practice a little bigger since the app actually needs to do something. Similarly on iOS.