On plasma-6.5, the display of wallpaper or screen fill with color is broken in the session login screen. Operating System: ROSA Fresh Desktop 13 KDE Plasma Version: 6.4.80 KDE Frameworks Version: 6.17.0 Qt Version: 6.9.2 Kernel Version: 6.16.4-generic-1rosa13-x86_64 (64-bit) Graphics Platform: Wayland Processors: 8 × Intel® Core™ i7-7700K CPU @ 4.20GHz Memory: 32 ГиБ of RAM (31.2 ГиБ usable) Graphics Processor: NVIDIA GeForce RTX 3050 Manufacturer: Gigabyte Technology Co., Ltd. Product Name: B250M-D3H
Can confirm. Looks like due to https://invent.kde.org/plasma/libplasma/-/commit/c7e0ba9bb929c0bc6817cc676235d036f5ac04da Kscreenlocker was changed accordingly in https://invent.kde.org/plasma/kscreenlocker/-/commit/20ae1bb06d658eb8f32256df9b1f6d70adc870f5 But plasma-login-manager hasn't been.
*** This bug has been marked as a duplicate of bug 507842 ***