Add smoked oysters, crab meat, clams, peas, carrots, celery, potatoes, whatever you like to the stock. If you add potatoes, add them after they’ve been mostly cooked through. Feel free to use some of the potato water instead of stock. If adding carrots and celery, put them in with the onions.
I love a thick soup, so would add a low carb thickener when its almost done. If you like a thick soup too, add about 2 tablespoons of flour to the onions when they have softened, stirring to mix. Just before you add the stock.