cordova-plugin-wkwebview-cookie-sync
While this plugin has not been tested properly so far it should provide an alternative way to sync cookies in a wkWebView implemantation.
This is necessary as cookies may not get synced properly on the very first start of the app.
Usage
document.addEventListener('deviceready', () => {
wkwebview.injectCookie('mydomain.com/mypath');
});