>If the background lighting is fixed like an led or lcd display
This hasn't been true of LCD displays for years. They now use LED backlighting, and the backlighting is dynamic (it varies in brightness depending on what'd displayed, and changes across the display too).
>If you're using dark mode to save battery on a laptop it's not working.
My business class just-retired-to-k3s-duty laptop was manufactured in 2014 and has a LCD. That was only 5 years ago. Fixed backlight, no light ambience sensor.
Cheap laptops today like the HP Pavilions of the world still use fixed-backlight LCDs as well.
This hasn't been true of LCD displays for years. They now use LED backlighting, and the backlighting is dynamic (it varies in brightness depending on what'd displayed, and changes across the display too).
>If you're using dark mode to save battery on a laptop it's not working.
This is only true if your laptop is circa 2005.