Apple will no longer support web apps that use UIWebView. The apps and libraries need to be migrated to use WkWebView.

The latest Ionic already uses WkWebView, but several Cordova plugins still rely on UIWebView which is a problem.

https://ionicframework.com/docs/v3/wkwebview/

If you’re using Ionic you need to upgrade to iOS Cordova 5

cordova platform remove ios
cordova platform add ios@5.0.0

Also you might need to remove additional plugins that use UIWebView such as inappbrowser.

cordova plugin rm cordova-plugin-inappbrowser

More information about the breaking changes can be found here:

https://cordova.apache.org/news/2018/08/01/future-cordova-ios-webview.html