Deprecate KLineEdit::passwordMode
Support for (globally) configuring NoEcho or ThreeStars as password input mode has disappeared from the config UIs in recent years, so nobody might be using the non-default modes these days. Also are many dialogs at least in KDE software instead already using KPasswordLineEdit or a plain QLineEdit with hardcoded echomode (QLineEdit::Password usually) or a QtQuick password field, which are also ignoring any global workspace-wide settings. So in the absence of consistent usage of a globally configurable secrets input mode that option no longer makes really sense (and perhaps also never made), so this feature can just be removed from the API.
Some places also might gain from using KPasswordLineEdit instead, by now having the option to make the password visible on demand, as also recommended by KDE HIG:
Provide a “Show password” checkbox to unmask the password both when setting new and when entering existing passwords.
From https://develop.kde.org/hig/components/editing/lineedit/