This is a barebones lockscreen with a password input box. Note that you MUST have pamtester installed or you won't be able to log in.
pamtester
You can run the lockscreen with quickshell -c shell.qml.
quickshell -c shell.qml
You can run the lockscreen in test mode (as a window) with quickshell -c test.qml.
quickshell -c test.qml