Observable is deprecated in rxdart 0.23.1

Rxdart no longer needs a custom class to work.

It now relies on extension methods, which is a recent Dart feature (Dart 2.6) to implement all of the Observable features directly on Stream.

You can safely replace all your Observable by Stream.

Use Rx.combineLatest2 rather than Observable.combineLatest2

Observable no longer work!

The Observable can be replaced by Stream as I mentioned in the question but if you are using methods like combineLatest2 from Observable, then just replace Observable by abstract class Rx so you can use Rx.combineLatest2