I’ve always been certain that the echo created by an Echo Knight fighter using their 3rd-level feature Manifest Echo is not defined in game terms as a creature, since the description of the echo never explicitly tells it is a creature. But the presence of people believing the echo to be a creature in lieu of the fact that it is immune to all conditions and might make saving throws (game characteristics typically associated with creatures only) brought this doubt to my mind.
This tweet from Jeremy Crawford implies it is just an image and not a creature, further confirming that the feature should tell you, but this other tweet implies that the echo is an object whilst the feature doesn’t explicitly say so.
(Included for reference and insight, since tweets are not eligible as official ruling)
Is the echo a creature?