I agree about the processing time of commercial yogurt.
If you make yogurt with regular milk and allow it to incubate for a minimum of 12 hours, the lactose level will be negligible.
I have a friend who is severely lactose intolerant and has no problem with yogurt made this way and allows hers to incubate for longer, 18 hours, as I recall.
One caveat. Not all people who think they are lactose intolerant are sensitive ONLY to lactose. There are other components in milk, i.e., some of the proteins, that also will cause digestive upset. One of my grandchildren (teenager) has this and the symptoms are dose related. That is, she can tolerate a small amount of dairy products in baked goods, etc., but at a certain level she develops symptoms.
Macaroni and cheese or bread pudding is not tolerated but baked goods (scones, cakes, etc.,) containing milk or cream are okay.
If you use half and half or light cream to make yogurt, you will get a product that substitutes for sour cream but has little or no lactose. This too should be incubated longer than 12 hours.
