Is/was there ever an ethnic cuisine that didn't use salt in their cooking?

Yes. Yes indeedy, indeedlydo!

Whatever it was my mother used for cooking. She did not add salt when cooking anything. She was born in France and had a heritage of Polish/Belgian/etc. etc. (multinational). In later years she added salt only in small amounts if a recipe called for it. I have followed in similar manner, as has my sister.

My father, a chef and at one time a caterer, wasn't a salt adder either. He came from a mix of Indigenous (a.k.a. native american) and something else (nobody seems to know what, as he was adopted). He was fond of adding garlic and pepper among other things to enhance food flavor. I follow this method most often as I don't do well trying to follow the stringent guidelines of recipes.

In general, I'd figure cuisines with a few (or a multitude) of spices/seasonings, would be less likely to add in salt.

I've veered off to the land of chile pepper and black pepper sesame seeds and a japanese concoction called Nanami Togarashi that I don't re member where I got it, except it was in California, and now I need more...
but I still do use salt some of the time. More a smidgen than I used to, for sure. Same with sugar, but I cut that quite a lot. The bottle of Nanami Togarashi is so old that the ingredients may have salt and I don't know it.

Interesting, Sturgis, and I think you're right.

I've also veered off of potato chips and similar, by now way off. They are beginning not to beg me to buy them in the store, all the pretty packages.