I have seen rice milk made from rice flour.
I have seen almond milk made from dry finely ground almonds.
I have seen soy milk made from boiled mashed soy beans (soy milk is similiar, but different to, the whey biproduct formed by making soy-based cheese and/or tofu)
How do you make lactose-free milk from finely ground bleached wheat flour?
There are a variety of grain milk recipes...easy to find on the internet. None that I know of use finely ground flours. Wheat needs to be cooked to make it digestible. You would have to cook the wheat first. This would be a straining nightmare. You could, however use wheat berries, cooking them first. Alternately, you could use flaked wheat, which has been cooked and rolled.
By the way, soy milk is really the starting point of tofu, before the coagulant is added.
Since wheat flour has to be cooked before consumption, your best bet is to make a very watery pudding. Use some very low ratio - I would go for 10 g flour per liter of water - and then proceed like a standard starch pudding. The ratio is an educated guess, you would have to experiment to get the best thickness.
To get somewhat closer to the milk mouthfeel, add some fat, about 3% would be right. I would use a good quality margarine, but some neutral vegetable oil would also work. If you also add a little bit of sugar, it will make the result more pleasant.
It won't taste exactly like milk, but it will be as closest as you can get, if you have to use wheat flour.
