The subclass feature Manifest Echo explicitly covers attacking from the Echo’s location when taking the Attack action or when taking a specific reaction:
When you take the Attack action on your turn, any attack you make with that action can originate from your space or the echo’s space. You make this choice for each attack.
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.
My Echo Knight picked the fighting style Superior Technique with the Combat Maneuver Brace. This gives my fighter a new trigger for using a reaction:
When a creature you can see moves into the reach you have with the melee weapon you’re wielding, you can use your reaction to expend one superiority die and make one attack against the creature, using that weapon. […]
If I understand correctly, this would mean when an enemy enters my Echo’s reach, it does not trigger Brace, because it isn’t mentioned as possible scenario’s for attack from the Echo’s location. Is this interpretation correct?