I have a, I think, interesting theory about echo endings. About which ending is real. But before I start, I warn you that there will be a lot of spoilers for Echo and Arches.
Apparently, the developers of the game said that there is no one true ending. Every ending is canonical because it's kind of like a multiverse or a time loop.
The important thing, however, is that Arches exists. Arches is an independent game but is still a continuation of echo and still based on some of its interpretation of the echo game and its endings.
So, answering the question which ending is true, we answer which ending is true for Arches, i.e. for the true echo continuation.
The second important thing for a game where we have a time loop is running in circles.
An often repeated line in the game is that "you are running in circles". Of course, this refers to the player and the spirit of Samuel who controls the fate of Chase. Each time we make different choices and we have different endings but in the end nothing changes. We're still in a circle.
I'll start with the Arches events and Echo events.
In Arches, two characters important for the plot appear. This is Brian and Duke. If they're alive, that means they couldn't die in the echo.
Brian dies in Leo's route, killed in a cave. This is what happens if we pick up a gun in the fight scene with Brian. This makes the two final endings (good and bad) false. This, however, means that the ending where Brian kills us may (but does not have to) be true.
Brian also dies in Jenna route. This makes both endings of this Route false.
In other Routes, Brian does not die. This makes Carl's 3 endings, Leo's 1 Ending, Flynn's Ending and TJ's Ending possible to be true.
The second character is Duke. His death is always linked to the theft of Chase's car. He gets killed by the socket man every time he tries to escape.
In Carl Route, if Jenna stabs us, we see a car and a dead person. It's probably duke. The events of this Route are probably an illusion. Our death breaks this illusion. This means Duke is probably dead in Carl's other endings, but we don't see that.
Duke dies in Flynn and Jenn's ending in exactly the same way.
That leaves us with two endings. End of TJ route and our death by Brian in Leo route.
Now we're going to look at the second important issue, which is running in circles. There is another repeated phrase on this point. That is: They always come back.
Where are they going back to? To the loop. What is a loop? Chase keeps returning to echo. Or otherwise, Sam's return to Echo. Sam is the real main character of the game but he is hidden. This is us as a player.
We as players come back over and over again. And we can do it all the time, but our control ends when it comes to the ending.
For Samuel, the goal is to get out of the echo. However, the death of chase will not result in an escape. How do we know that? Samuel had previously possessed Sydney and Sydney's father. They are both dead, but Samuel's soul continues to circle and possess other characters. Duke also says in one of the Routes that killing doesn't fix things, so he doesn't want to kill Chase but learn from him how to stop the madness. Samuel's soul will just pass on to another person.
The only way to stop everything is for Samuel to escape. It was he who caused evil to appear in the echo. Escape is his goal in every Smoke Room Route. Escape will stop evil.
Therefore, the real ending must be TJ route.
This is the only ending where Chase escapes from Echo before being attacked by mass hysteria. This is the only ending where Brian and Duke live. Duke's death is linked to Chase's car theft and an escape attempt. He can't do it because chase has left. Brian never goes to the mine and he never kidnaps Chase so he stays alive too.
Sam broke free from the echo and Chase did not return to the echo. We know this because in the epilogue after TJ's ending, Chase does not appear. Chase also does not appear in arches.
However, mass hysteria continues to echo after Chase's escape. Why? Here comes another sentence: this city needs secrets.
I believe in the bathroom scene, Chase is talking to the city and the city's bad guy himself. The figure in the mirror is the essence of what this city is. The secret that Sydney was killed by Chase has never been revealed. Brian's brutal murders were never revealed either. Secrets are the thing that keeps this city alive and this city is trying to make sure we don't know the secrets.
Escaping the wheel saved Chasea and Samuel. It led to the fact that the city almost completely died after his departure and was almost forgotten. Only crazy ghost hunters remember this cursed place. Evil, however, lives on because the secrets have not been revealed. Revealing secrets is our goal at arches.
This theory has several holes. One is the events in the epilogue after the TJ ending are different than in the arches.
However I can explain by simply changing the idea slightly by the developers and not suggesting which ending is real. Another option is that events happen a little differently in the real version of TJ's ending but still similar to what's in the game. This makes TJ's ending not true, but it's closest to the truth. Chase's elopement with TJ could be real.