SUMMARY In the system settings, you can change the language of the entire system (System Settings → Region & Language → Language (Modify) → Change Language), but it lacks a search feature like in Android or GNOME. Adding a language search feature would be especially helpful for users who are testing different setups (since changing the language also affects sorting).
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/5141
Git commit 6a1f113609e1f92088676c0a70e6fc7cf0e12578 by Nate Graham. Committed on 31/01/2025 at 13:00. Pushed by ngraham into branch 'master'. kcms/region_language: add search field to language chooser sheet Plus a bit more keyboard navigability, since it now makes extra sense with focus placed in a search field by default. FIXED-IN: 6.4.0 M +50 -6 kcms/region_language/ui/AdvancedLanguageSelectPage.qml https://invent.kde.org/plasma/plasma-workspace/-/commit/6a1f113609e1f92088676c0a70e6fc7cf0e12578