I understand chickens need grit. Is it in purina layena? Would oyster shell be considered grit? How about sandy loam soil that they eat? is that grit? Or do I need to buy a bag of grit? Was keeping chickens this complicated back in the Day?
If your chickens are free ranging they really do not need grit. They will pick up tiny pebbles that serve the same function. if they are cooped for any length of time without outdoor access they will need grit.
bluie is correct. As long as they have access to the ground/dirt every day they don't need grit.
If you want to offer grit you buy it separately from feed and oyster shell and offer it in a separate container. The chickens will take what they need. If you are concerned about them getting enough grit from your run you could offer some and see how much of it they use.