While attempting to lock the KDE session, Lightdm fails to load properly at random, resulting in the instruction screen to switch to TTY to unlock the session from terminal.
We no longer use lightDM, having moved to SDDM several years ago. As such, this bug report is no longer applicable. Bugs reports for the new SDDM-based login screen should be filed to one of two places: 1. Visual/UI bugs with the login screen UI itself, or feature requests: plasmashell | Theme - Breeze 2. Bugs with the login/user switching process: https://github.com/sddm/sddm/issues