Hi Stefan,
Not having a solution for you, just background information.
this is not (directly) related to your plugins. It has to do with the fact that Cordova uses the UIWebview as the HTML rendering engine, and that Apple previously announced UIWebView’s deprecation in June 2018. Beginning with iOS 12, they began warning developers about migrating to WKWebView, UIWebView’s successor.
More background info:
https://cordova.apache.org/news/2018/08/01/future-cordova-ios-webview.html
Even version 5 of cordova does not have WKWeView support, you can read in https://cordova.apache.org/announcements/2019/02/09/cordova-ios-release-5.0.0.html
So this is more a Cordova issue, that could become painful for OutSystems mobile applications.
Wonder if someone from OutSystems Engineering has more information on this topic.
Regards,
Daniel