At my company we have multiple Flutter Apps in production. The experience has been quite good so far. In fact we are converting some of our native projects to Flutter in order to reduce the maintenance burden.
I'm not primarily a mobile dev but have done enough Android/iOS appdev to prefer Flutter. Even if it was only for the Android version of an app, I'd choose Flutter over Android APIs because it's so fragmented and janky in its own ways. RN to me is the worst of both worlds (React + Android quirks).
Of course it depends on the app, if it has specific not-run-of-the-mill UX requirements. It's also better to start with Flutter (or RN) rather than switch from something else, as the feel is so different users would be put off by the change. Each is fast/slow in different places/ways.
Upgrading old RN version to new RN version has always been a very painful experience. Flutter in our experience has been easier to upgrade.
Also Flutter has support to call native APIs using platform channels. (https://docs.flutter.dev/platform-integration/platform-chann...)
At my company we have multiple Flutter Apps in production. The experience has been quite good so far. In fact we are converting some of our native projects to Flutter in order to reduce the maintenance burden.