As far as I know Ukraine doesn't have any net neutrality regulations. Since net neutrality is per country then I think it's sort of a moot point. I also think you'd have a hard time arguing that pulling the plug violates net neutrality. You're effectively treating all traffic the same in that there is no more traffic. I do think it would be interesting to see how that would play out though.
Aside from that Ukraine would have to go after Musk for it. Which seems like a really bad idea if you want to remain in favor with the increasingly unstable power broker that controls the infrastructure you need.