A simplified WKWebView view controller with workarounds for setting cookies.

WorkaroundWebViewController.swift

import UIKit
import WebKit

class WorkaroundWebViewController: UIViewController, WKNavigationDelegate {
    let request: URLRequest

    private let websiteDataStore = WKWebsiteDataStore.default()
    private var webView: WKWebView!
    private var initialDummyNavigation: WKNavigation?
    
    init(request: URLRequest) {
        self.request = request
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        configureWebView()
    }

    private func configureWebView() {
        let configuration = WKWebViewConfiguration()
        configuration.websiteDataStore = websiteDataStore
        webView = WKWebView(frame: .zero, configuration: configuration)
        webView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(self.webView)
        
        // We pin the web view to the safe area because some pages break otherwise.
        NSLayoutConstraint.activate([
            view.safeAreaLayoutGuide.leftAnchor.constraint(equalTo: webView.leftAnchor),
            view.safeAreaLayoutGuide.rightAnchor.constraint(equalTo: webView.rightAnchor),
            view.safeAreaLayoutGuide.topAnchor.constraint(equalTo: webView.topAnchor),
            view.safeAreaLayoutGuide.bottomAnchor.constraint(equalTo: webView.bottomAnchor)
        ])
        
        webView.navigationDelegate = self
        initialDummyNavigation = webView.loadHTMLString("", baseURL: nil)
    }

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        if navigation == initialDummyNavigation {
            initialDummyNavigation = nil
            setCookiesAndLoadRequest()
        }
    }
    
    private func setCookiesAndLoadRequest() {
        let cookies = HTTPCookieStorage.shared.cookies ?? []
        
        websiteDataStore.httpCookieStore.setCookies(cookies) {
            self.loadRequest()
        }
    }

    private func loadRequest() {
        webView.load(request)
    }
    
    // Errors
    
    func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: Error) {
        showAlert(for: error)
    }
    
    func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
        showAlert(for: error)
    }
    
    private func showAlert(for error: Error) {
        let alert = UIAlertController(title: "Error", message: "\(error)", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
        present(alert, animated: true, completion: nil)
    }
}

extension WKHTTPCookieStore {
    func setCookies(_ cookies: [HTTPCookie], completion: (() -> Void)?) {
        let group = DispatchGroup()
        for cookie in cookies {
            group.enter()
            setCookie(cookie, completionHandler: {
                group.leave()
            })
        }
        
        group.notify(queue: .main) {
            completion?()
        }
    }
}