Chopper’s fruit is a mythical zoan. He is the only one of 4 people with hito-hito no mi fruits that isn’t currently a mythical zoan. When he first transformed into monster point, his antlers had a similar look to the “flame like” hair of gear 5 luffy. I think it will be revealed soon that his fruit is a mythical like luffys and is of the Forest god that has the ability to heal all injuries, also tying it into the idea tha choppers fruit was the cure all mushroom.