Just remember. Cats are carnivores so they can't survive living a vegan diet

Um.. I'm fairly certain that my two vegan cats are very much with us.
They eat veganpet dry food with is equipped with artificial taurine.
Sure they are alive, they are basically being fed the human equivalent of tofu and vitamin supplements every day.
Do they get any wet food? Cats aren't big on drinking water so it's important to add fluids to their food, whether it's wetting their dry food or giving them fresh or canned food. They can develop kidney problems apparently from the lack of fluids.
I can't bring myself to feed mine veganpet so I buy organic free range lean meat and sustainable fish for my cat & dogs. They get that with fresh vegetables and brown rice or pasta, our hens eggs, molasses, sometimes berries and also seeds like sunflower and pumpkin.
I think the least you can do is provide them with a natural diet and not support factory farms. If you can find a small scale local organic farm that would be even better.
If dogs or cats left to fend for themselves would kill to survive anyway so the best we can do is provide them with as humane & environmentally as possible natural options.
We also buy the 'waste' products such as liver, necks etc I feel a bit more comforable with this as the animal wasn't generally killed for these products they are merely 'left overs'
I have a couple of fussy eaters who turn their noses up at dry food & anything canned at the best of times so doubt I would have much luck with veganpet.