How to configure a useable screen locker in Awesome+LightDM+NixOS?

I've been using Awesome+LightDM with the GTK greeter on Arch Linux for some years, and I'm in the process of moving to NixOS. One issue with this has been the screen locker. I've mapped Windows-l to light-locker-command --lock . When activating that the screen goes black, then turns off. To get back to LightDM I have to press Ctrl-Alt-F7 and wait for about 10 seconds while some weird message about "being redirected to the unlock dialog" displays. I've tried installing and enabling both the "gtk" and "mini" greeters (not at the same time), but after restarting X neither of these seem to be used. How do I set either of them up? The relevant part of the configuration : services = { xserver = { displayManager.lightdm.enable = true; enable = true; layout = "us"; libinput.enable = true; windowManager = { awesome.enable = true; default = "awesome"; }; xkbOptions = "compose:caps"; xkbVariant = "dvorak-alt-intl"; }; }; I also tried enabling programs.slock, but that doesn't integrate with lightdm.