From what I can tell. I've not used Tauri and it's been years since I've tried flutter.
Tauri currently has poor support for mobile and Linux (because of the state of WebkitGtk).
Flutter uses Dart which is not widely used for anything else. Harder to learn as there is no MDN, w3schools or standard spec for it. Also Flutter Web has issues due to it's use of Canvas over the DOM.
IMO, electron is still the way to go for cross platform apps.
Tauri currently has poor support for mobile and Linux (because of the state of WebkitGtk).
Flutter uses Dart which is not widely used for anything else. Harder to learn as there is no MDN, w3schools or standard spec for it. Also Flutter Web has issues due to it's use of Canvas over the DOM.
IMO, electron is still the way to go for cross platform apps.