The Earth One book series from DC Comics tells small-universe comics about the first days of superhero characters Batman, Superman, Teen Titans, Wonder Woman and more. There is no cross continuity with any of the other DC titles, they stay self-contained. They don't even cross over with each other.
Because the world of Earth One is described as having the "Earth 1" designation on the DC Multiverse Map.
And on the final page of last week's Superman #14, with the many captures Supermen across the Multiverse… we see a special capsule for Earth One.
Although that Superman doesn't seem to match that of Earth One. Does it count?