Okay, support for IE11 security fixes will continue for years to come, but support for earlier versions is now completely gone. Microsoft has moved all development to the new Edge web browser.  Also, the new Office 365, Teams, and Microsoft 365 services only support Edge, Chrome, and Firefox web browsers.
 
As of November 30, 2020 Teams will completely stop supporting Internet Explorer. Other Office 365 and Microsoft 365 services will officially support IE11 until August 17, 2021. However, we have already noticed that some SharePoint Online functionalities do not work on IE in the same way as Edge or Chrome browsers, so it is high time to get to know the Edge browser.

What happens if an internal application depends on Internet Explorer functionality?

IE is part of the Windows 10 operating system, and at least for now, Microsoft has not set a deadline for ending support for IE11 patches. In addition, Edge has "IE Mode" for the browser, which means that if a service requires IE functionality, Internet Explorer can be run in the Edge window. The user interface is simpler for the employee.
 
IT professionals who want to prepare their business for the end of IE11 support should read this Edge Deployment Guide