use this package:

https://pub.dev/packages/flutter_internet_signal

import 'package:flutter_internet_signal/flutter_internet_signal.dart';

void main() async {
  final FlutterInternetSignal internetSignal = FlutterInternetSignal();
  final int? mobileSignal = await internetSignal.getMobileSignalStrength();
  final int? wifiSignal = await internetSignal.getWifiSignalStrength();
  print('Result dBm -> $mobileSignal');
  print('Result dBm -> $wifiSignal');
}