Starting November 30, 2020 the Teams web application will no longer support Internet Explorer 11 while all other Office 365 services will stop supporting Internet Explorer 11 starting August 17, 2021.
Starting March 9, 2021 Edge legacy will no longer get updates and as such will also stop being supported for Office 365 access.
If you don’t have yet started moving to a modern web browser – either Google Chrome or Edge Chromium, now is a good time to start.