結論

画像と文言系はまだ大丈夫ですが、ボタンとか入力フォームとか認識されないので、工夫する必要があります。
XDで設計したUI

生成されたFlutterのソースコードのUI

生成されたFlutterのソースコード

import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';

class IPhone12ProMax1 extends StatelessWidget {

  const IPhone12ProMax1({
    Key key,
  }) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: const Color(0xffeabbd4),
      body: Stack(
        children: <Widget>[
          Transform.translate(
            offset: Offset(134.0, 134.0),
            child: Text(
              'Sign Up',
              style: TextStyle(
                fontFamily: 'Helvetica Neue',
                fontSize: 40,
                color: const Color(0xffe4e4e4),
              ),
              textAlign: TextAlign.left,
            ),
          ),
          Transform.translate(
            offset: Offset(61.0, 258.0),
            child: Text(
              'Email',
              style: TextStyle(
                fontFamily: 'Helvetica Neue',
                fontSize: 30,
                color: const Color(0xfffffafa),
              ),
              textAlign: TextAlign.left,
            ),
          ),
          Transform.translate(
            offset: Offset(61.0, 408.0),
            child: Text(
              'Password',
              style: TextStyle(
                fontFamily: 'Helvetica Neue',
                fontSize: 30,
                color: const Color(0xfffffafa),
              ),
              textAlign: TextAlign.left,
            ),
          ),
          Transform.translate(
            offset: Offset(61.5, 350.5),
            child: SvgPicture.string(
              _svg_mo2c82,
              allowDrawingOutsideViewBox: true,
            ),
          ),
          Transform.translate(
            offset: Offset(62.0, 686.0),
            child: Container(
              width: 295.0,
              height: 70.0,
              decoration: BoxDecoration(
                borderRadius: BorderRadius.circular(27.0),
                color: const Color(0xfffdf5f5),
                boxShadow: [
                  BoxShadow(
                    color: const Color(0x29000000),
                    offset: Offset(10, 20),
                    blurRadius: 10,
                  ),
                ],
              ),
            ),
          ),
          Transform.translate(
            offset: Offset(158.0, 704.0),
            child: Text(
              'Sign up',
              style: TextStyle(
                fontFamily: 'Helvetica Neue',
                fontSize: 30,
                color: const Color(0xff000000),
                fontWeight: FontWeight.w700,
              ),
              textAlign: TextAlign.left,
            ),
          ),
        ],
      ),
    );
  }
}

const String _svg_mo2c82 =
    '<svg viewBox="61.5 350.5 295.0 150.0" ><path transform="translate(61.5, 350.5)" d="M 0 0 L 295 0" fill="none" stroke="#fffdfd" stroke-width="3" stroke-miterlimit="4" stroke-linecap="butt" /><path transform="translate(61.5, 500.5)" d="M 0 0 L 295 0" fill="none" stroke="#fffdfd" stroke-width="3" stroke-miterlimit="4" stroke-linecap="butt" /></svg>';