The library 'package:flutter/material.dart' is legacy, and should not be imported into a null safe library
The fix for this is relatively simple.Just go to your pubspec.yaml file and make sure the lottie dependancy that you have there, is the latest version as on the pub.dev site.
Use dart pub outdated --mode=null-safety and then dart pub upgrade --null-safety to upgrade all your dependencies to null-safety.
For more details go to https://dart.dev/null-safety/migration-guide.
go to https://pub.dev/packages/font_awesome_flutter,
copy the latest release version of font i.e in my case (font_awesome_flutter: ^9.1.0),
then add it to your pubspec.yaml file i.e (font_awesome_flutter: ^9.1.0),
click pub get dependencies
go to your input_page file
click get dependencies