That is actually an interesting question: is it natural for chickens to stop laying eggs in the winter? Or is that just something they do when we keep them in parts of the world where winter days are so short?
Chickens are descended from Red Junglefowl.
https://en.wikipedia.org/wiki/Red_junglefowl
"In many areas, red junglefowl breed during the dry portion of the year, typically winter or spring. This is true in parts of India, Nepal, Thailand, Vietnam, and Laos. However, year-round breeding by red junglefowl has been documented in palm-oil plantations in Malaysia and also may occur elsewhere."
(wikipedia has lots of links to sources of that. But notice, it mentioned breeding in WINTER.)
Here is an article about feral chickens on the island of Kauai (descended from domestic chickens, but living like wild animals with no human care.)
https://www.livescience.com/57669-animal-sex-kauai-chickens.html
It says that some of them do breed all year long, while others are seasonal.
I would assume that no-one is making an effort to provide supplemental light for those feral chickens.
I agree that artificial light is not natural. But it's not natural to keep chickens in areas with heavy snow in the winter, either. They would naturally starve to death or freeze, so humans provide food and shelter to let them stay alive and hopefully healthy anyway. And it's not natural to keep chickens in areas with very short winter days, which leaves the question of how much light is really best for chickens in winter-- it may be more than what some climates can naturally provide. I would think is reasonable to add artificial light in winter up to at least 10 or 11 hours of light per day, just to allow the chickens enough time to eat and move around. (Yes, that is quite a ways from the 16 hours that is sometimes recommended to increase laying.)