From walkthroughs, I know that I have to speak to Jonah and Uchu in the Skull Cave to begin the mission. But when I go there, they're present but I can't talk to them. They aren't highlighted as conversation targets.
This confuses me, because I've already done the DLC misson "The Dragon and the Prince", which shows up to the right of "The Path of Fear" on the Path Skills screen. Did I somehow miss the mission? Do I have to advance further in the story? (I have not yet spoken to Etzli in Upper Paititi.)