when you use the Builder widget, it has its own context, therefore the values inside it won't get updated as you expect. Because they are not part of the Getx's widget tree.
As of the day that I am writing this tip, Feb 2023, Flutter File Dialog works flawlessly in both Android and iOS. If the file_picker package does not work for you then give this one a little try. You will not regret it.
music picking on iOS using File Picker flutter package works ok in real devices because they have the Music app, but it does not work on emulators since they dont. so dont panic. just test it on a real device.