There is nothing about ethical veganism that guarantees a healthy diet. Vegans can eat just as badly as omnivores but without cruelty (except to themselves). And don't bother whining that you think that vegans shouldn't eat imitation meat if they don't want to eat real meat!. That is the most profoundly lame and unthought-out position that you can possibly take! Vegans don't stop eating meat because they don't like it. They stop eating meat because it causes unnecessary harm to our fellow sentient beings (not to mention its significant contribution to climate change).
So anyway, if you want to eat a plant-based burger and you're in a hurry, here are my recent findings!
Burger King. On their website, BK is thoughtful enough to walk you through the Impossible Whopper and makes clear that if you want it vegan, you need to ask for them to hold the mayo.