system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel Cinematic Universe] What is the "official story" regarding how everyone came back?

It makes sense the the truth, which is that Time Travel is possible and the Avengers borrowed the stones from the past, is a dangerous secret that the Avenger wouldn't want getting out; It would pose the danger of someone else copying their results and becoming a god.
gpt
Since Jimmy Woo, Darcy, and Monica Rambeau all know the events of Endgame's final battle with Thanos in pretty significant detail (including Wanda almost defeating Thanos singlehandedly and Captain marvel almost defeating him until Thanos used the Power Stone against her), it's likely that Iron Man's, War Machine's, or Spider-Man's suits were recording the events of the battle, and that information was shared or leaked with the public. It's why Tony is so idolized in Far From Home (see the graffiti, etc.). (Alternatively, one of the more talkative or public-friendly heroes like Scott Lang or Professor Hulk may have gone on a press tour to explain what happened.) You could argue that perhaps only the government got this information, but the fact that Darcy knows about it despite not being a member of a government organization implies that the information has gotten out to the general public.

So it's possible that the quantum realm van is known about, and almost confirmed that the existence of the Infinity Stones is known about, but whether time travel was ever made clear or what the Infinity Stones actually are was ever explained to the public at large is unknown. It's likely that the Avengers explained the Infinity Stones to some extent during the 5 year gap between IW and Endgame to explain how everyone vanished, but time travel may still be a secret, especially since the Avengers are the only ones to figure it out, and they still needed Pym particles which, as far as we know, only Hank Pym knows how to produce.

So the official story is likely something incredibly close to the truth but with perhaps a few key details omitted.