Try adding scaffold key

lib/src/controllers/flap_controller.dart

@@ -2,6 +2,10 @@ import 'package:flutter/material.dart';
 import 'package:libadwaita/src/widgets/adw/flap.dart';
 
 class FlapController extends ChangeNotifier {
+  FlapController([this.key]);
+
+  final Key? key;
+
   bool isOpen = true;
   bool isModal = false;
 

lib/src/widgets/adw/new/scaffold.dart

@@ -7,6 +7,7 @@ import 'package:libadwaita_core/libadwaita_core.dart';
 class AdwScaffold extends StatefulWidget {
   const AdwScaffold({
     super.key,
+    this.scaffoldKey,
     required this.body,
     this.flap,
     this.flapStyle,
@@ -24,6 +25,8 @@ class AdwScaffold extends StatefulWidget {
     this.controls,
   });
 
+  final Key? scaffoldKey;
+
   final Widget body;
 
   final Widget Function(bool isDrawer)? flap;
@@ -90,6 +93,7 @@ class _AdwScaffoldState extends State<AdwScaffold> {
           ),
           Expanded(
             child: Scaffold(
+              key: widget.scaffoldKey,
               drawerEnableOpenDragGesture: _flapController
                       ?.shouldEnableDrawerGesture(FlapPosition.start) ??
                   false,