A simple package that uses url_launcher to launch the maps app with the proper scheme on all platforms.
On iOS, map links as specified by Apple are launched. On Android, the geo intent is used as documented here. For web and other platforms, the plugin will simply launch Google Maps.
import 'package:maps_launcher/maps_launcher.dart';
...
MapsLauncher.launchQuery('1600 Amphitheatre Pkwy, Mountain View, CA 94043, USA');
MapsLauncher.launchCoordinates(37.4220041, -122.0862462);
Consult the table provided by the url_launcher documentation to see which SDK versions maps_launcher supports.