If you want something like this.
Create Layer Copy (Background Copy)
Select By Color Range (in this pic I selected the background)
Invert Selection.
Make the Selection into a Work Path (right click the selection > Make Work Path)
Set the tolerance to 1 or 2 pixels, In this I chose 1 px.
Make a new blank layer and fill it with white.
You should see the outline.
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You can leave the blank layer transparent if all you want is the lines. Then you can turn of visibility of the underlying layers.
Or you can choose whatever color you like for the background color. If you choose another color, especially a darker color, you will want to make the path active then use Stroke Path and select the width and color of your choice for your outline.