So when you say "banned" weapons, it really depends on how you look at it. Not banned for Ukraine because they didn't sign it, or banned because a handful of powerful nations signed it and a somewhat large number of smaller less powerful states signed it.
Just pointing out that just because you may see/hear some media outlets use that term, doesn't mean that it is precisely true...or even mostly true for countries around the world.
89 parties to the convention out of 196(ish) total countries, so a little less than half.
It would, on the other hand, be banned to have targeted civilians intentionally (although the inherent right to self defense would allow to fire back at enemy fire originating from a populated area...although the legality can get murky here).