When running in GNOME, we'd monitor the state of the screensaver. That doesn't work in non-GNOME desktops, as implementors of org.gnome.ScreenSaver will get started, such as gnome-screensaver and cinnamon-screensaver, neither of which offer the API we expect anyway.
See https://bugs.launchpad.net/ubuntu/+source/cinnamon-session/+bug/1803078