Dart version is 2.2.0 but I get an error requiring version >=2.2.0

The output of dart --version is completely irrelevant for Flutter. What you need to check is flutter doctor -v or flutter --version. In your case it shows Tools • Dart 2.1.2 (build 2.1.2-dev.0.0 0a7dcf17eb)

You probably need to switch to another channel until the next stable channel update

flutter channel dev

or

flutter channel master

Flutter has its own dart-sdk in flutter/bin/cache/. So when you do dart --version , its probably another dart sdk in your system.