First , flutter uses an architecture similar to a game and uses it's own rendering pipeline and Layout system, meaning integrating with anything that exists is extremely challenging ( Chartings , Lottie etc... ) you'll be often waiting behind the Flutter team to implement the feature inside the engine.

On top of that the SDK supports for Darts right now are non-existent, maybe it'll change in the future , but Firebase + GCloud is pretty much all you'll get in terms of SDK as of now.