I have heard positive things about both carnivore (zero carb) and  keto with MS in various videos over the last 15 months or so but have no personal experience. Here is a quick Youtube search that might have some information.

https://www.youtube.com/results?search_query=carnivore+diet+and+ms

https://www.youtube.com/results?search_query=keto+and+ms

https://www.youtube.com/results?search_query=keto+low+carb+diet+and+ms

From what I have learned if I had MS, I would definitely try a very strict ketogenic diet or maybe even a carnivore diet. But that is just me and I am not a doctor so this is not medical advice. But if I had a severe disease my thought would be "what would it hurt to try?". If that answer was "not much risk for possible good reward" I think it would be a no-brainer. A month would probably see results if there were going to be any. I know my diabetes and joint pain was 80-90% resolved in two weeks, at least a major turn in the right direction. Then more accumulative results over time.

Carnivore is mostly a more extreme version of keto although there are nuances as it is possible to eat enough protein that a person will not be in ketosis. I personally would try the carnivore for two weeks and see if I was feeling any better with fewer symptoms. If so keep going. If it works and a person felt they just had to have vegetables work some in one at a time and see if symptoms come back. But that is just what I would do. Not recommending it for anyone else. Do your own due diligence.

Wife and I are eating mostly meat and eggs now with only a very few vegetables. A fair amount of cheese. The vegetables don't seem to bother me much but she avoids a lot of stomach issues if she avoids vegetables. We started out keto with a lot of green above ground vegetables and the diet did wonders for our health not to mention a lot of weight loss. But over time we find lowering the vegetables even more is additionally helpful. Probably because of correcting stomach problems from years of food abuse. Younger people might not have the same results as we have had. Over time as we become even more metabolically healthy we may be able to incorporate more vegetables back into our diet. They do not cause major issues for us now, just minor ones. Just feel better when she does not eat them. Less bloating and better energy. More regularity.

John