Flutter web generates the index.html of new web projects which always includes the following meta tag:

• flutter/packages/flutter_tools/templates/app_shared/web/index.html.tmpl

  Line 20 in c1872f9

  <meta content="IE=Edge" http-equiv="X-UA-Compatible">

That header used to be set to force the newest rendering engine possible on Edge (pre-Chromium)...

Is it doing anything nowadays? Is it there to prevent Internet Explorer mode? Is it needed?

No, so we should probably remove it from our index.html files.