There is dry food available which is grain free. Also watch for other carbs... Tractor Supply has an allegedly grain-free dry food, but it is perhaps not low enough in carbohydrates since they use potatoes in it.
Innova Evo is one premium food that has a grain-free dry food available, and there are others out there. Read labels.
You generally don't want to feed dry food exclusively over the years, since that may lead to slow dehydration, predisposing the poor cat to renal failure.
I try to feed my cats canned food (whether cat food or human-grade canned fish or other stuff) at least once per day. I leave out dry kibbles for free feeding.
Remember that cats evolved as desert animals, and they get some of the moisture they need by drinking the blood and body fluids of their prey. I guess this is why they love canned food which has gravy on it.
I found that feeding cats canned human-grade fish (such as salmon, tuna, sardines, or mackerel) will cure and prevent dry eyes. Apparently the EFAs in oily fish are utilized by mammals' bodies directly in mucous membranes, which the eyes have.
Good luck!
I agree about fresh and canned. There are some great cat food brands like Weruva.
No kibbles. They don’t need it and many manufacturers put “mammal msg” in the kibble to get the cats addicted to non-nutritious food. Rats and other rodents smell this ingredient from miles away and come to choose your house because of it.