We spent a month in Paris last year. We are both vegan. We get places with kitchens. That said, we did go to the Marais three times for falafel sandwiches. Sigh. Well, it was so good the first time that we had to return to make sure it wasn't a fluke. The nearby bakeries, also sigh.
Denis is fond of pizza, and as I am not, he just got some take-out from Hank's Vegan Pizza. He would recommend it. Hank also has Hank's Vegan Burgers, but we never got there. https://www.hankrestaurant.com/
Some of the outdoor markets have prepared foods. The Moroccan tangines at Enfants Rouge looked wonderful, but we never had good timing. There were also prepared offerings at Popincourt, which is where we did most of our produce shopping, and Bastille.
One day we went out for South Indian, but I don't remember the name of the restaurant.
A friend from my vegan discussion forum went this may and drooled over these places. I doubt she'll mind my sharing them.
https://www.cloudcakes.fr/
https://www.vgpatisserie.fr/
https://monepicerieparis.fr/
She speaks fluent French, and said the Vietnamese places were also quite good. She's fond of the sandwich I believe is called Bahn Mi. Apparently one must be mindful of the fish sauce.
Yes, Happy Cow can be your friend.
Donna