I could maintain weight eating any low-carb diet I feel like, I see another probable problem. If one cuts out lactose for a long time, they probably will feel bad when bringing them back, to some extent, at least. It’s quite natural for an adult and it did happen with my SO and many other people, I’ve heard that a lot of times. I, on the other hand, still can handle lactose but I still subtly feel it’s not ideal for me if I don’t keep them minimal (and I guess it was always the case, I just never knew what is it like without it). After very-very close to zero lactose years (I ate little amount of butter and half-hard and hard cheese and very occasionally some other dairy), it seems, my body doesn’t want most dairy back, it feels a bit wrong. The close to zero stuff feels okay, I never had any problem just because I ate some butter or harder cheese but I am careful with other dairy, even if I use something, it’s rare and the amount is tiny, it’s okay for me. Just like with carbs, I judge if it’s worth it.
Weight maintenance is a complicated thing, not only our diet matters, of course. In some cases, certain items matter a lot and in other cases, it’s just about calories, who knows why (but the diet easily can affect calories, of course. It doesn’t always do but usually it does). No one can say what will happen in your case (but making educated guesses is nice, I am not nearly that knowledgeable).