In this guide, I am telling you where you can find the Legendary Wakja Boar in Red Dead Online. 

Location; 

Firstly, you will need to go to the following location. It is between Quacker’s Cove, and the Lower Montana River. 

You can also find it in the other area near Thieves Landing. They will also spawn here. 

It is recommended you do this without a horse because it may scare your horse and you will die quickly. The recommended method is to get on the top of the mountain and start shooting, once you spot it. You can also naturalize it with tranquilizers. 

If you are with the group, then only one person can get the skin. So it is recommended that you should do it alone. 
Do not trust your horse, you may get knocked off by it and you will die. So sit on the top of the mountain and wait for it to spawn and then you can kill it.