Flutter isn't yet at a 1.0 release. It looks very cool and I'm excited about it personally, but compared to React and Swift it has less stability and far less tooling support and developer knowledge. There's also reason to believe that it could be abandoned by Google down the line: it's being developed by the Dart team, but it's inherently at odds with the Android team because it circumvents their API almost entirely.
I'd do a personal project in it, but I wouldn't start a business on it right now.
I'd do a personal project in it, but I wouldn't start a business on it right now.