I think the sixth wall break is when the movie implies that the world watching it is part of the same metauniverse as the movie.

For example Everything Everywhere All At Once has Evelyn go to a universe where she is a movie star, and it has clips from Michelle Yeoh's real life history as a movie star.

The idea behind Everything Everywhere All At Once is that everything and everyone is connected so the people watching the movie are all Evelyn/Jobu Tupaki in another life.

Another example is The Matrix Resurrections where Neo is making a version of the Matrix video game and the conversations he has with his captors mirrors the conversations that Lana Wachowski had with her producers when they were pressuring her to make the film. And there are parts of the movie where it seems as though Neo is trying to "wake up" the viewers of the movie into realising that their own experience of "real life" is part of the Matrix.