WKWebView in SwiftUI iOS 14 and Xcode 12

I am in a similar boat where I have a SwiftUI app that wraps a WKWebView in UIViewRepresentable.

For your goal of updating font-family and size, I am using a WKUserScript to inject custom CSS to change the font-family and size. This is working OK for me on both iOS 13 and 14. Sample code that creates my WKWebView in my UIViewRepresentable class.:

Code Block swift
    lazy var webView: WKWebView = {
        guard let path = Bundle.main.path(forResource: "style", ofType: "css"),
          let cssString = try? String(contentsOfFile: path).components(separatedBy: .newlines).joined()
        else {
          return WKWebView()
        }
        let source = """
           var style = document.createElement('style');
           style.innerHTML = '\(cssString)';
           document.head.appendChild(style);
        """
        let userScript = WKUserScript(source: source, injectionTime: .atDocumentEnd, forMainFrameOnly: true)
        let userContentController = WKUserContentController()
        userContentController.addUserScript(userScript)
        let configuration = WKWebViewConfiguration()
        configuration.userContentController = userContentController
        let webView = WKWebView(frame: .zero, configuration: configuration)
        return webView
    }()

However, I have a different problem - now my WKWebView doesn't render for about 30 seconds on iOS 14. I have no idea, and stumbled upon this question trying to research an answer. Let me know if you have encountered this.

I ran into an issue where I am calling WkWebview.evaluateJavaScript:@"navigator.userAgent" and it is taking 20 seconds to return in Beta 4. Maybe that is what you are running into.

Seems to work OK if you are running on Big Sur