Like Raster says, there’s a lot of crap soy produced in the west. I can’t see how heated miso soup could be probiotic either. A better soy product would probably be natto, which is eaten raw so the bacteria remain alive, and it contains vitamin K2, B12, mucilage and a useful enzyme called nattokinase. It tends to taste awful to anyone who doesn’t happen to be Japanese though. Soy is high in plant proteins, which tend to be toxic, and it also contains goitrogens that can interfere with your thyroid function. It’s probably best to avoid it until you’re feeling better.
Kimchi and sauerkraut are good options, but also contain goitrogens, like all crucifers. The important thing is to make sure your iodine status is good. Goitogens essentially “steal” iodine from your thyroid, so eating a bit more overcomes this. Seaweed is the best source of iodine, but kelp supplements are a cheap and reliable way to maintain good iodine levels and contain a few other nutrients.