The Ancestral Guardian barbarian feature Ancestral Protectors (XGtE, p. 10) reads as follows:
Starting when you choose this path at 3rd level, spectral warriors appear when you enter your rage. While you’re raging, the first creature you hit with an attack on your turn becomes the target of the warriors, which hinder its attacks. Until the start of your next turn, that target has disadvantage on any attack roll that isn’t against you, and when the target hits a creature other than you with an attack, that creature has resistance to the damage dealt by the attack. The effect on the target ends early if your rage ends.
Assuming I have a fighter dip, what would happen if I hit a creature then used BA to rage? Would the ancestors target the creature I hit at the start of my turn even though rage was initiated after the hit?
If I then action surged and hit something else, would they target that?
I’m specifically wondering if you can use booming blade to trigger the ability RAW.