Marvel's main universe is 616 and is pretty straightforward, but DC's main universes are a bit complicated. So what are the main universes of the DC Universe?

We know Batman Beyond, Red Son, etc., are alternate universes, so what are the main universes?

Earth-21 - New Frontier
Earth-22 - Kingdom Come - main?
Earth-23
Earth-30 - Red Son
Earth-31 - All-Star Universe
Earth-353
Earth-44 - Metal Men
Earth-51 - Utopia
Earth-9 - Tangent
Earth-A - Lawless League
JL 3000
Pax Batmana
Polyester Age
Post Crisis
Post Flashpoint
Animated Universe
Earth-43 - Red Rain
Injustice
New Order
One Million
2020
2965
2999
All-Star Superman
Earth -44
Earth One - Post Crisis
Earth-0
Titans Tomorrow
Earth-1 - Pre Crisis - main?
Golden Age
Earth-14 - Assassins
Earth-15 - Legacy Earth
Earth-16 - The Just
Earth-2 - Post-Flashpoint - main ?
Earth-2 - Pre Crisis - main ?