• Plasma's Login Experience Need Improvement: Works okay in basic case but is barebones and can't handle more. Desktop experience should support edge cases.
• What is Wanted: Great out-of-box experience in multi-monitor, high DPI and HDR; keyboard layout switching; virtual keyboards; easy CJK input; display and keyboard brightness control; full power management; screen readers; pairing trusted bluetooth devices; login to known Wi-Fi for remote LDAP; remote support from startup.
• A Brief History: In Plasma 5, KDM was retired in favor of SDDM. SDDM was modern at the time using new QML but had problems.
• SDDM's Big Architecture Problem: Designed for a single greeter window with arbitrary QML. Needs more tight integration for wishlist features. Power management is reinvented and can't integrate with other Plasma features easily. GNOME's GDM is the gold standard by running half a Gnome session. SDDM's Wayland support also had issues.
• Theme Problems: Mistook writing UI in a high-level scripting language with themability. QML contains business logic and is not the best for customization. Poor for end users, theme developers and Plasma developers.
• The Plan: Oliver Beard and the author made a new multi-process greeter using the same startup mechanism as the desktop session. Intend to expose familiar settings and bring design in line with screenlocker. The backend is based on SDDM stripped down to cover future needs and incubated in the KDE ecosystem.
• Current State: Implemented in two new repositories - Plasma Login Manager and Plasma Login. Works and is at feature parity but not ready for distros to package yet. Screenshots look similar to stock Plasma SDDM setup.