As you can see, when I apply my normal map to my tileset (all tiles selected using atlas), the behaviour of Light 2D changes unprovoked, going from a simple modulation in the light area to a sort of birds eye view of a cone light.
I am unsure why this is, as I'm not really versed in this sort of thing but I guess it could be a driver issue, as I have not tried updating them, but it almost looks intentional. Is this a feature i'm unaware of?
the normal map used is that of the entire tilemap, as instructed. It has a bit of alpha on all its pixels.
Normal map import settings:
size limit: 0
normal map: enable
fix alpha border: off
premult alpha: on
hdr as srgb: off
(tile size: 128x90)
Light 2D appears to be affected regardless of whether shadows are enabled or not.