Unable to create new file outside of Documents folder with Flutter

DCIM maybe is part from media or photos

so try this if work, I do usually include in my manifest

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
 // try to add this 2 lines
<uses-permission android:name="android.permission.READ_MEDIA_IMAGES"/>
<uses-permission android:name="android.permission.READ_MEDIA_VIDEO"/>
 // Optional to add this 
 <uses-permission android:name="android.permission.ACCESS_MEDIA_LOCATION"/>

and setting my gradle as like this

  android {
     compileSdkVersion 33
     ....
     // from deafult config 
     defaultConfig{
      ...
      mindSdkVersion 28
      targetSdkVersion 33

  }

then for permission you can either put them on list just in case when requesting

 // You can either call this in initState or any listener you have
 // as long ass it can be triggered first on page
 static Future<void> requestStorageorPhotos() async{
    await [
       Permission.photos,
       Permission.storage,
     ].request();
    // try to listen from its changes permission
    if((await Permission.photos.status.isGranted) || (await 
      Permission.storage.status.isGranted)){
      // Do your thing if allow
    }else{
     // or anything in here from not allowing it.
    }
  }