https://wccftech.com/windows-10-21h2-insider-preview-build-21387-retires-ie11/

Microsoft has released Windows 10 Insider Preview Build 21387 for Insiders in the Dev Channel. The build officially retires Internet Explorer 11 desktop application and turns off Task Manager's “Eco mode” feature.

The company made the Windows 10 May 2021 Update, version 21H1, available to the public earlier in the week. While version 21H1 is a minor update, the next Windows 10 21H2 is expected to be a major feature update, focusing on visual changes and improvements.