Is there a way to set up a screen locker, so that it takes me back to whatever greeter I use when I need to login again? I am using Xorg and typical options like xscreensaver etc. use a separate login mechanism
You might be able to make something using a separate greetd instance, where the final login command is basically just a chvt back to the running session. I have not tried doing this myself. Otherwise, for Wayland the ext-session-lock-v1 protocol provides for fail-locked screen locking, ruling out crash-to-unlock bugs. That is the class of bugs that make all X-based lockscreens quite unsafe by design.