I have the same problem, I fixed like that:

Fist, I make a class and write all of function I use:

// /src/common/utils/web_alternative.dart
void usePathUrlStrategy() {}

dynamic get window => null;

After that, I use it to import:

// When I want to use html
import 'package:vinh/src/common/utils/web_alternative.dart' if (dart.library.html) 'dart:html' as html;
// When I want to use usePathUrlStrategy
import 'package:vinh/src/common/utils/web_alternative.dart' if (dart.library.html) 'package:flutter_web_plugins/flutter_web_plugins.dart' show usePathUrlStrategy;

I can use that like it:

if (kIsWeb) {
  usePathUrlStrategy();
  html.window;
}