Well, for a start, not something covered in 20 varieties of artificially coloured sugary icing.
Just a ring of deep fried dough dusted with sugar. Or a ball of the same dough filled with jam and deep fried. Stop.
Jam-filled donuts are popular in N.A., too, but they're called "jelly doughnuts" and are usually cut in flat squares or circles rather than being round, for some reason.
Doughnuts started out here mostly just rolled in sugar. Then came the sugar glaze (my favorite) which is a sugar syrup that dries to a crackly, slightly sticky sweetness. The glaze led to flavored glaze, which led to frosting. My two favorite frostings are maple (very big in Canada, obviously, but also for some reason in the Pacific NW of America) and chocolate. I can leave off the pink icing with sprinkles.
It's interesting that the Guardian article you link to about donuts does not include any rings, just dough balls. No one knows who invented the ring donut (or when, for that matter), but it was an obvious idea to increase the crispy fried shell while also making sure there was no soggy uncooked dough in the center. In North America, doughnuts probably came from the Dutch settlers with their "oily cakes" but those were definitely round balls and not rings.