A coordinator implementation I use In my projects [Used for one main coordinator, you can change it to work with multiple coordinators]

Coordinator.swift

import UIKit

protocol Coordinator {

    var navigationController: UINavigationController? { get set }
    // config funcs
    func setNavControler(_ navCtrl: UINavigationController) -> Self
    func start()
    // display funcs
    func show(view: AppScreen)
    func showMainViewCtrl(animated: Bool)
    func back()
    var activeViewController: AppScreen { get set }
}

MainCoordinator.swift

//
//  MainCoordinator.swift
//  InprisWay
//
//  Created by Yonathan Goriachnick on 13/10/2020.
//  Copyright © 2020 200apps. All rights reserved.
//

import Foundation
import UIKit

class MainCoordinator: Coordinator{
    
    internal var navigationController: UINavigationController?
    internal var activeViewController: AppScreen = .mainScreen
    
    class func shared() -> MainCoordinator {
        return sharedManager
    }
    
    private static var sharedManager = MainCoordinator()
    
    private init() {}
    
    func start(){
        showMainViewCtrl(animated: false)
    }
    // set the nav bar
    func setNavControler(_ navCtrl: UINavigationController) -> Self{
        self.navigationController = navCtrl
        return self
    }
    
    func show(view: AppScreen){
        activeViewController = view

        switch view {
            case .settingsListScreen:
                let vc = SettingsListViewController.instantiate()
                vc.settingsViewModal = SettingsListViewModal()
                push(vc)
            case .aboutScreen:
                let vc = AboutViewController.instantiate()
                push(vc)
            case .mainScreen:
                showMainViewCtrl(animated: false)
            case .settingScreen(let type):
                let vc = SettingViewController.instantiate()
                vc.viewModal = SettingViewModal(type)
                push(vc)
            case .searchScreen(let settingItems):
                let vc = SearchableListViewController.instantiate()
                vc.settingItems = settingItems
                vc.modalPresentationStyle = .pageSheet
                navigationController?.topViewController?.show(vc, sender: true)
            default:
                break
        }
        
    }
    
    internal func showMainViewCtrl(animated: Bool){
        activeViewController = .mainScreen
        let vc = MainViewController.instantiate()
        vc.viewModal = MainViewCtrlViewModal()
        navigationController?.pushViewController(vc, animated: animated)
    }
    
    func back(){
        navigationController?.popViewController(animated: true)
    }
    
    var topViewController: UIViewController?{
        return navigationController?.topViewController
    }
    
    func push(_ vc: UIViewController){
        navigationController?.pushViewController(vc, animated: true)
    }
}

UsageExample.swift

class Usage{
  // setup coordinator in AppDelegate or SceneDelegate
  let navController = UINavigationController()
  MainCoordinator.shared().setNavControler(navController).start()

  // AppDelegate or SceneDelegate setting
  // config window
  let window = UIWindow(windowScene: windowScene)
  window.rootViewController = navController
  self.window = window
  window.makeKeyAndVisible()
  
  // show screen
  MainCoordinator.shared().show(view: .aboutScreen)
}

// apps' views -> we can also split into separate enums for each child coordinator
enum AppScreen {
    case loginScreen
    case agreementScreen
    
    case mainScreen
    case navigationScreen
    case callScreen
    case radioScreen
//    case aboutScreen
//    case messagesScreen
    
    case settingsListScreen
    case settingScreen(_ type: SettingType)
    case searchScreen(_ settingItems: [SettingsPresentable])
    case aboutScreen
//    case messagesSettings
}