Nishta is the only veggie place in Dubrovnik (and the non-veggie places have very limited veggie options), so we went there a few times as it was the only thing keeping me alive! The veggie burger was pretty delicious and the bill came in a little treasure chest with a bean with a smiley face on it!
It’s very small! So you’ll definitely need a reservation if you’re eating in the evening. I reckon they seat 8 inside and another 8 outside!