So, the question is regarding the Lucky Feats 2nd use.
You can also spend one luck point when an attack roll is made against you. Roll a d20, and then choose whether the attack uses the attacker’s roll or yours.
Would that function as the Echo? Since the Echo is technically also you, but from a dying timeline that didn't happen.
Matt Mercer: An Echo Knight is able to tap into those dying timelines and temporarily pull a version of themselves and use it to fight alongside them.
This is also slightly supported by the fact that all the echo's rolls from attack rolls to saving throws is modified as if it were your real body's rolls. What are people's thoughts about this?
Or is it as simple as "If I have the Lucky Feat, well so does my Echo."
Clarification on the Sentinel Feat part: "When you hit a creature with an opportunity attack, the creature’s speed becomes 0 for the rest of the turn."
combined with the Echo's: "When a creature that you can see within 5 feet of your echo moves at least 5 feet away from it, you can use your reaction to make an opportunity attack against that creature as if you were in the echo's space."