Juglans Nigra (eastern black walnut) which is probably the most widespread walnut in north america, though there are like a half dozen other species.
Probably also what you'd see labeled "American walnut" in Europe. They taste stronger than juglans regia (eurasian walnut), but the shells are way harder, so it's trickier to grow as a crop.
Looking at walnut jam, it looks like it might be a lot of work, but maybe I'll try next year. https://foragerchef.com/cooking-with-green-walnuts/