~~"So we have to make do with just locally foraged foods from native plants."
Really? Why?
Before gardens, people were opportunistic eaters. You ate everything that was available. If you can build a fire, you can place a flat rock over it. Add a little grease you have saved from the last bear you found or killed, and you have a nice way to cook whatever comes your way. Grasshoppers, worms, grubs from fallen/rotted trees, whatever you caught in traps or nets, birds/mice/squirrels/groundhogs, etc. Or you can use an animal's stomach or bladder as a pot. Hang it over a fire and fill with water for stews and soups. Or hang the "pot" and drop heated rocks into the water. You'll get a very fast boil. Add some wood ash for salt flavor and herbs you gather and whatever meat you found, and you have a great meal. Or go simple and eat the worms, etc., raw. Or spear them on a stick, to hang before a fire.
Before gardens, people had much more varied diets. But what they ate was far more dependent on seasons and weather. If you found a dead deer or managed to kill one, you gorged on meat. If early Spring, you ate lots of young skunk cabbage. People did dry lots of food, laying it in the sun to dry or hanging it in the rafters of their lodge, and that helped in times of snow. But, mostly, they enjoyed feast or famine. The better your family or community "witch" or herbalist, or your wandering hunter, was at their knowledge and job, the fewer occasions of hunger.