We went on a Thursday for lunch and the buffet was about 90% vegan, except for two vegetarian dishes. I was hesitant to take my omni friends there but they absolutely loved it! For 4 euros you get 3 choices, a small salad plate and free water. Ask the chef what's not vegan and he'll tell you.
TIP: Go to the upstairs seating!!! They have those low tables with pillows and it's very charming :)