1. Using Dartpad.dev load flutter counter sample.
2. Update the app title to include Unicode characters (in this case th in upper script)
3. Find the line in Myapp class with: home: MyHomePage(title: 'Flutter Demo Home Page' ),
4. and change to: home: MyHomePage(title: 'Flutter Demo Home Page \u1d57 \u02b0' ),
5. run the code - title is shown as but the last two characters are shown as boxes with x inside the box.

This worked before update to Flutter version 2, and it still works for some Unicode characters i.e. \u22C5, so not sure why it is not working for all valid Unicode characters.