I’m past level 50 (level 53) and I have the Heart of Azeroth necklace, but Nathanos Blightcaller doesn’t have the Breaking Kul Tiran Will quest available, which is part of the The First Assault questline.
I’m trying to unlock the Mag’har Orcs.
Have you completed Uniting Zandalar?
mmm no I don’t think so. What is that?
It’s the quest to unlock world quests. (It’s also required before you can start the main part of the War Campaign.)
The other requirement is to complete the 3 foothold quests. (If you’ve already unlocked world quests on a character, this isn’t required.)
All of that will come from Nathan’s or other NPCs near him on the boat. So, do any quests you find there (that aren’t dungeon quests.)
It does look like there are some bugs with scaling right now, so some quests might not show up until 60.