What is the expected outcome
The display to show both on the laptop and monitor.
What output did you get
the boot process seems to get to the display manager and then just goes to a black screen with a white underscore in the top left. Except if I have an external monitor plugged in - in which case it displays fine there.
If the monitor is plugged in before display manager runs during the boot process - a display will be generated on it (even if it’s later unplugged and then plugged back in). Otherwise nothing is shown on the monitor. Regardless - the same black screen with a white underscore is shown on the laptop.
Meta information
nixos-version = 24.05