As it is, when an application built using ArcGIS Experience Builder Beta is opened in Internet Explorer, the user sees a blank screen and an error is thrown, which is only seen if you open the console.
It would be great if the user directly got a message 'Browser not supported' or similar.
Please refer to the Frequently Asked Questions:
Which browser is recommended for the beta testing?
The chrome browser is recommended for this beta testing. IE11 and below are not supported.
Maybe end users who want to stick with IE should consider to upgrade to v12...?
I imagine Herdis' request is for the end users who still have to have IE on their machines due to outdated IT practices and aren't savvy enough to look in the Developer Tools for the console log.
It is indeed to help the end users
This is a question for Esri - as a solution I will make a redirect page that checks browser before it continues to the experience.