This did not work for me.
Jan 12 23:25:16 nixos systemd[1]: Starting Display Manager...
Jan 12 23:25:16 nixos systemd[1]: Started Display Manager.
Jan 12 23:25:17 nixos systemd[1]: display-manager.service: Main process exited, code=exited, status=1/FAILURE
Jan 12 23:25:17 nixos systemd[1]: display-manager.service: Failed with result 'exit-code'.
Jan 12 23:25:17 nixos systemd[1]: display-manager.service: Triggering OnFailure= dependencies.
Jan 12 23:25:17 nixos systemd[1]: display-manager.service: Failed to enqueue OnFailure= job, ignoring: Unit plymouth-quit.service not found.
Jan 12 23:25:17 nixos systemd[1]: display-manager.service: Consumed 1.388s CPU time, 193.5M memory peak, 222.4M read from disk, 76K written to disk.
Jan 12 23:25:18 nixos systemd[1]: display-manager.service: Scheduled restart job, restart counter is at 1.
Jan 12 23:25:18 nixos systemd[1]: Starting Display Manager...
Jan 12 23:25:18 nixos systemd[1]: Started Display Manager.
Jan 12 23:25:19 nixos systemd[1]: display-manager.service: Main process exited, code=exited, status=1/FAILURE
Jan 12 23:25:19 nixos systemd[1]: display-manager.service: Failed with result 'exit-code'.
Jan 12 23:25:19 nixos systemd[1]: display-manager.service: Triggering OnFailure= dependencies.
Jan 12 23:25:19 nixos systemd[1]: display-manager.service: Failed to enqueue OnFailure= job, ignoring: Unit plymouth-quit.service not found.
Jan 12 23:25:19 nixos systemd[1]: display-manager.service: Consumed 1.391s CPU time, 80.8M memory peak, 76K written to disk.
Jan 12 23:25:20 nixos systemd[1]: display-manager.service: Scheduled restart job, restart counter is at 2.
Jan 12 23:25:20 nixos systemd[1]: Starting Display Manager...
Jan 12 23:25:20 nixos systemd[1]: Started Display Manager.
Jan 12 23:25:21 nixos systemd[1]: display-manager.service: Main process exited, code=exited, status=1/FAILURE
Jan 12 23:25:21 nixos systemd[1]: display-manager.service: Failed with result 'exit-code'.
Jan 12 23:25:21 nixos systemd[1]: display-manager.service: Triggering OnFailure= dependencies.
Jan 12 23:25:21 nixos systemd[1]: display-manager.service: Failed to enqueue OnFailure= job, ignoring: Unit plymouth-quit.service not found.
Jan 12 23:25:21 nixos systemd[1]: display-manager.service: Consumed 1.417s CPU time, 80.8M memory peak, 76K written to disk.
Jan 12 23:25:22 nixos systemd[1]: display-manager.service: Scheduled restart job, restart counter is at 3.
Jan 12 23:25:22 nixos systemd[1]: display-manager.service: Start request repeated too quickly.
Jan 12 23:25:22 nixos systemd[1]: display-manager.service: Failed with result 'exit-code'.
Jan 12 23:25:22 nixos systemd[1]: Failed to start Display Manager.