I made a Flutter package that might help with this question called fxf.

To create the text you've written above, you can do the following:

import 'package:fxf/fxf.dart' as fxf;

class MyWidget extends StatelessWidget {
  ...

  final String text = '''
~(0xff7c65c4)!(3,0,0xff7c65c4)Same!(d)~(d) 
*(5)!(1,0,0xffff0000)textfield!(d)*(d) 
`(1)different`(d) 
~(0xffe787cc)!(1,0,0xffe787cc)styles!(d)~(d) 
''';

  Widget build(BuildContext context) {
    return Center(
      child: fxf.Text(text),
    );
  }
}

Which produces the following result: image of text with multiple styles

For example, on line ~(0xff7c65c4)!(3,0,0xff7c65c4)Same!(d)~(d), style command ~(0xff7c65c4) changes the text color to a light purple, while ~(d) returns the text back to its default black color. Likewise, !(3,0,0xff7c65c4) adds a strikethrough solid line with the same purple color, and !(d) removes it.

More info on the style commands can be found on the fxf readme.