I haven’t tested any of this, so, please just take this in the spirit of suggestion: miso adds a nice umami to this soup, which has to be replaced (without a soy product). I would suggest trying fresh ginger and/or lemongrass paste. If you’re comfortable with the sea side of things, you could use a dashi broth, or perhaps add some seaweed (some brands make roasted seaweed snacks, which I sometimes crumble into soups). (Kombu dashi and seaweed are vegan.) For the vinegar, you could just use a little bit less of white vinegar (rice vinegar is usually milder than other grain-based vinegars). If you have trouble with all vinegars, you might consider citric acid, which is a powder that can be added to recipes, similar to salt. It adds a really nice sour note, and could stand in for vinegar. You can find vitamin-bottle sized citric acid in the canning aisle, or at a vitamin store (and Amazon).