Things to consider
Here are some tips and tricks for you to learn from my mistakes in setting up a flutter environment. These mistakes are sometimes tedious to fix.
Feature or version conflict
This error comes into play if you have some error while running the "flutter run" command. The error message tells something like "language feature is disabled for this library".
This means that there is usually a version conflict. Here the version of the package in the file "pubspec.yaml" must be checked first.
Otherwise the dependencies can also be lifted with "flutter upgrade" to the newest version.
If running the app still causes errors, clearing the cache can help.
Dependencies can be deleted and cleaned up using "flutter clean". These are then reinstalled with "flutter run".