I've read articles over the years on growing amaranth--a high-protein grain--as well as small backyard plots of wheat. See if your state agriculture department has a newsletter with ads. Georgia does, and heirloom bean seeds are often advertised for sale, or in their "wanted" section. Did I forget sunflower seeds and peanuts? Those are two great sources of protein. I'm personally partial to garbanzo beans, if you can grow them successfully. Fresh, they taste like a fresh unroasted peanut, but with only 2/3 of the calories, and make great hummus, salad dressing, snacks, calderita (Philippine stew) or various Latino or Middle-Eastern dishes, including falafel. Baker Creek Heirloom Seeds sells both heirloom beans and foreign seeds, and their catalog is a work of art. Don't know about flaxseed, but I love the stuff in bread or sprinkled on salad. A weaver might purchase the flax plants, as is, for linen at a good price?
Happy gardening adventures!