@carl I know I said, "you're probably right"...
Meanwhile, the CMake files for #systemsettings make no mention of the #KUserFeedback library, I know, I looked and even built it from source myself, to check.
On the bright side, I can read emails from GitHub and GitLab and other sites again in the newer #Evolution, the one that shipped with #Disco had decided that white text on a white background was the way to go, while this #Eaon version manages black text on a white background.