ALL fully vegan places in Riga. They are not many, but I recommend to visit them all. If you have time to visit just one, I'd suggest Kozy Eats for food. And OneCaCaco for cacao.
I only add places here, where there are at leat 3 vegan options. Some of them are also just Vegan/Vegetarian places.
If you want perspective from others, also foreigners who come to Riga, here are some blogs I found.