Got lucky with one from a 3rd party but it doesn't turn off the screen when I close the cover like my old phone case did. I assume that had a chip in it or there's a software setting I've not found.

Samsung was pretty much one of the only manufacturers installing hall sensors under the display to detect the magnets in their flip cases. I think they stopped including that sensor around the time they got rid of the hardware home button. Their latest tablets still do include a case sensor AFAIK, not sure if it's the same hall effect one or something else though.

As a side note I miss those cases with the small window, was pretty cool to be able to just flip the lid, see the time, then stuff the phone away