Since a few month Flutter stable release support web assembly: https://docs.flutter.dev/platform-integration/web/wasm
Currently the latest published version of flutter-maps-launcher does not support web assembly.

I haven't checked in detail, but I think that for "flutter-maps-launcher" to be compliant it would only need to migrate to package:web.
https://dart.dev/interop/js-interop/package-web

I am willing to contribute if needed.