>>Low-fat fermented dairy

Why just low-fat? For the microbiome, I'd expect that pretty much any fermented food (sauerkraut. real pickles, kimchee, yoghurt low-fat and high, fermented soy, kefir) is a positive to varying degrees.

As far as fermentation reducing lactose allergenicity, we need to separate an allergy to lactose from the inability to digest lactose (no lactase). Fermentation reduces lactose by a good bit, making it more edible for the intolerant. As far as the allergic, many of those folks are reacting to something called A1 protein which is a relatively recent development (associated with breeds that produce more milk per day than the others). The original, discovered later, is called A2. Worth checking out if you're allergic to dairy.