Boiled jackfruit seeds are a plain and simple snack that is made at home. I don't recall seeing the seeds for sale on the street. When you prepare ripe jackfruit, each pocket of the yellow fleshy "fruit" surrounds a large seed. That seed is edible, once cooked and peeled.
The simplest preparation is just to boil the seed and peel the thin husk. The boiled seeds taste like a combination of boiled potato and taro. It's soft and creamy. You can enjoy them plain!