Kale chips are real easy to make and hold whatever seasoning you want pretty well. I say kale because that’s the best one to search for if you’re looking online for recipes, but the recipes you’ll find work with pretty much any tougher leafy green. Imo mustard greens go particularly well with msg seasonings; when I make instant ramen, I usually make a slightly higher effort soup base, and the unused ramen seasoning packets almost always go to mustard green kale or chard chips. I’ve never tried to make them last longer than a week or so, but its a dehydrated salted food. I’m sure they’d last a good long while if you sealed them with some kind of preservative or dessicant or something