I don't think a dog is capable of agreeing philosophically with veganism, because dogs don't understand what slavery is. But dogs are capable of living healthy lives on a vegan diet
While it could naturally be possible to have a dog live on a vegan diet, I would never recommend that anyone does it without significant communication with veterinarians and other professionals in dog health. It is very easy to cause dietary deficiencies in your dog and cause very harmful, possibly irreparable damage in the process. It's also important to note that it's much more complex than just looking at nutrient contents since the way that a dog's body processes food differs significantly from how a human's does.
Dogs come from a long evolutionary line that has adapted to a diet that includes animal products for millions of years, haphazardly removing animal products from their diet without preventing the possible consequences for doing so is animal cruelty.
Well you see, vegans are people who don't like slavery, and don't eat meat or milk or eggs that come from slaves. Because vegans think eating the corpses of slaves is wrong
Plenty of suffering or dead dogs in the world because of self righteous idiots that think like you. Don’t own a carnivore if you don’t want to feed it meat.