In Red Dead Redemption 2 you can also find the Legendary Boar. It's in Bluewater Marsh.
The Ram moves within the area marked on the screen below.
What weapon to hunt the Boar with?
You can kill the Boar with two accurate gun shots. So, you don't have to worry about it. As soon as you notice him, use the Dead Eye, aim your shot and shoot at the target.
What does the fight with the Boar look like?
The boar is rather weak and shy. It will start running away as soon as you start shooting at it. It's worth using the Dead Eye and take a few accurate shots at your opponent.
What can I do with the Boar hide?
If you go to the Trapper you can create:
Legendary Beaver Flop Hat - you need boar and beaver hides and some feathers.
Legendary Boar & Bison Fowlers - you need boar pelt and 37 dollars.