This should be declared only once in the root view of the NavigationStack.

AllowsSwipeBack.Swift

import SwiftUI

extension View {
    /// Allows swipe back when navigation bar is hidden.
    /// This modifier should be applied to a view that resides within a NavigationStack.
    /// - Returns: A view that allows swipe back when navigation bar is hidden.
    public func allowsSwipeBackWhenNavBarHidden() -> some View {
        modifier( AllowsSwipeBackWhenNavBarHiddenModifier() )
    }
}

fileprivate struct AllowsSwipeBackWhenNavBarHiddenModifier: ViewModifier {
    func body(content: Content) -> some View {
        content
            .background{ NavigationControllerWrapper() }
    }
}

fileprivate struct NavigationControllerWrapper: UIViewControllerRepresentable {
  @MainActor
  final class ViewController: UIViewController, UIGestureRecognizerDelegate {
    override func viewDidLoad() {
      super.viewDidLoad()
      view.backgroundColor = .clear
      view.isUserInteractionEnabled = false
    }
    override func didMove(toParent parent: UIViewController?) {
      super.didMove(toParent: parent)
      if let navigationController = parent?.navigationController as? UINavigationController {
          navigationController.interactivePopGestureRecognizer?.delegate = self
          navigationController.interactivePopGestureRecognizer?.isEnabled = true
      }
    }
  }
  func makeUIViewController(context: Context) -> ViewController {
    .init()
  }
  func updateUIViewController(_ uiViewController: ViewController, context: Context) {
  }
}

Apply .allowsSwipeBackWhenNavBarHidden() to the root view inside your NavigationStack:

struct ContentView: View {
    var body: some View {
        NavigationStack {
           NavigationLink~~
            .allowsSwipeBackWhenNavBarHidden()
        }
    }
}