Are Vengeful Ancestors’ damage-dealing reactions enough to sustain the Barbarian’s rage?

To sustain their rage at the end of their turn, a Barbarian must have attacked a hostile creature since their last turn or must have taken damage since then. [PHB, pg. 48]

In the level 14 feature of the Primal Path of the Ancestral Guardian, "Vengeful Ancestors," the spirits called by the Barbarian’s rage may do force damage to a hostile creature. Mechanically, the Barbarian is using their reaction to cause this damage. [XGtE, pg. 10]

Is the fact that the Barbarian is using their reaction to cause damage to a hostile creature enough to sustain their rage? Or is this insufficient because the damage is not being caused directly by the Barbarian?

What could prevent a revenant monster’s Vengeful Tracker feature from working?

As I continue my campaign with revenants (as I mention in this question), I’m having some trouble:

The BBEG of my campaign is being tracked by a group of revenants as well as the party, but knows only about the revenant’s group. He is searching for a method to prevent those revenants from knowing where he is (via the Vengeful Tracker feature).

My guess is that all the things that can prevent a revenant’s Vengeful Tracker feature from working could also be used to kill the revenant permanently, but I want to be sure, so I’m asking you all whether I am right.