I have no idea what packages may be missing, but in Neon in the language module you can add languages, in KaOS there is only American English and if you press add there are no other languages.
Excuse my ignorance in these aspects, I am a basic user of KaOS.
And the translations are more complete in Kde Neon, maybe the version is newer than the one used by KaOS, but many dialogs in the control panel are in English, and in Neon they are in Spanish, which is the language I use.