Bug (Case 1342696) Can't assign sprite in localized asset reference in script LocalizeSpriteEvent.

I think this is a quirk in Unity. If you drag the root sprite asset into an Asset table then it will treat it like a Texture, you need to drag the sub asset which is the actual sprite. If you make the entry empty in the table you can see the asset type it expects in the corner. If it's Texture then it's the wrong type.