Dart plugin not installed; this adds Dart specific functionality. snap ubuntu code example
Example 1: Flutter plugin not installed; this adds Flutter specific functionality
Solution that worked for me:
1. Just install plugins.
Studio>>File>Settings>Plugins>Browse Repositories
2. Search for flutter.
3. Tap on Install (a dialog will pop regarding dart dependency. click Yes).
4. Once the installation is finished restart android studio.
If still not worked
1. flutter channel dev
2. flutter doctor -v
Example 2: Flutter plugin not installed; this adds Flutter specific functionality
ln -s ~/Library/Application\ Support/Google/AndroidStudio4.1/plugins ~/Library/Application\ Support/AndroidStudio4.1