I've stumbled upon a similar issue and thus on this question, however I also did find fixes for some of these issues. First, as you already pointed out, is base href="/" needs to be changed to base href="./" Second, the type="module" can stay in the script tag, so no need to change that. Last, in your Swift code you need to set a preference key on WKWebView so it's allowed to load other files (fixing the "access control checks"). webView.configuration.preferences.setValue(true, forKey: "allowFileAccessFromFileURLs") I guess you've already found fixes for your issues and I hope this would help others too.

Hi! I've had a similar issue the last few days and found that changes to the Developer License Agreement of our account had to be accepted. After accepting them, everything worked again. Hopefully this also solves your issue! Cheers, Dom