Is this functionality still available with ArcGIS Enterprise 11.x?
Also this URL only applies for text messages changes, is it possible to entirely customize the web page for an error?
https://support.esri.com/en-us/knowledge-base/customize-arcgis-web-adaptor-error-messages-000029282
Our end goal is to display a custom error message with a logo if a web adaptor URL hits an error!