We did soy with a stir fry and soy based yoghurt. The stir fry I put the smallest splash of low salt soy sauce in, took her portion out, then added more for the adult portions 😋 many bread products have soy flour in, so if you've tested wheat and any other allergens in the bread you could do toast. As others have said though, they can have cows milk and alternatives in food etc, it just can't replace formula or breastmilk. My LG has oat milk on her cereal :)
My little one had a soy yogurt, and as she now has been diagnosed with a lactose intolerance she has soy milk in her meals and with her porridge in the morning, which she has after her bottle so she doesn't often finish it all lol
It's ok to mix a little in her oatmeal. We introduced it as tofu. You could try something like that too.