With Sddm version 0.14.0 when you lock your screen you can't unlock it because you can't type your password. Password input is locked, keybord is not working.
Please report sddm bugs to sddm developers instead of kdm developer.
But I lock screen using KDE. I don't care what KDE is using to lock my screen.
KDM is long unmaintained, and distributions usually use SDDM. Even if you do not care, bugs for SDDM are not tracked at the KDE bug tracker, so reporting them here will not reach the audience you want to reach.