Removing ConfirmEdit class aliases (rECOEa8019493007e: Remove class_alias calls and cleanup Autoloads / https://gerrit.wikimedia.org/r/c/mediawiki/extensions/ConfirmEdit/+/1082578) requires updates to $wgCaptchaClass, otherwise the wiki crashes with errors like Error: Class "FancyCaptcha" not found.
If this is an intended backwards-compatibility breakage, then it needs to be in RELEASE-NOTES, and the documentation using old class names at https://www.mediawiki.org/wiki/Extension:ConfirmEdit needs to be updated.
If it is not intended, then there needs to be some back-compat code for the old $wgCaptchaClass values in Hooks::getInstance().