So I didn't read how to unlock because i didn't want to be spoiled, I understood that the bounty hunter lores were added after the final mission Join or Die because I found a new lore item in Hell or High Water and Listening without it being possible for me to missed them.

So I assumed they had something to do with Bridger w/e. I kept playing the game looking for these new lore items on every map.

Completed the set of bounty hunter, spammed join or die to get weapons, went to my character's list to equip my new weapons and then ... Bridger was there.

How is it possible to not be told something such important as unlocking a new character ?