Regression introduced in 11.2 final and present in 11.3RC1. The XWiki version 11.2RC1 and 10.11.7 are not affected.
Trying to upgrade leads to:
CKEditor WebJars are core extensions starting with XWiki 11.2 final and this prevents the upgrade. I don't see anything changed in the platform POMs regarding the dependency to the CKEditor Integration UI extension so I believe the regression is in the Extension Manager when building the XWiki distribution.