After discussing it with several contributors,…

After discussing it with several contributors, the decision has been made to officially remove IE11 support in WordPress 5.8.

The removal will be done in two phases:

  1. WordPress 5.8 (among other changes) will effectively remove IE11 support in the block editor and all generated CSS files used within the admin.
  2. WordPress 5.9 will focus on individual tickets that might be created to evaluate removing each instance of IE11 specific code.