One more vote here for flutter. Dart is not a language I’d want to use day by day but it gets the job done without getting much in the way. Tooling is great and there are a lot of libraries you can use for mobile platforms. Desktop support is a bit behind but is usable. You can also look into something like flutterflow.io to skip some boring parts of ui building. Haven’t used it much but since it allows you to export your code it does make building your initial pages much easier.