The password not matching warning comes up as the user is typing their password in the second box, this is distracting and will always be the case until the user finishes typing their password. Alternatively if waiting until the Create button is pushed isn't desired. The check could happen when the user stops typing for x seconds or milliseconds.
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/2345
Git commit a9c8b1917877d504c8e9c3967c7e60d4f156aa23 by Nate Graham, on behalf of Janet Blackquill. Committed on 22/11/2022 at 00:21. Pushed by ngraham into branch 'master'. kcms/users: debounce the password match message Users don't need to see that their passwords don't match until after they stop typing. M +10 -1 kcms/users/package/contents/ui/ChangePassword.qml M +10 -1 kcms/users/package/contents/ui/CreateUser.qml A +18 -0 kcms/users/package/contents/ui/Debouncer.qml [License: LGPL(3+eV) LGPL(v3.0) LGPL(v2.1)] https://invent.kde.org/plasma/plasma-workspace/commit/a9c8b1917877d504c8e9c3967c7e60d4f156aa23