Yes the game basically ends at U2 - and U3 is just U1 again.
If you want there is an alpha test for EverCraft2 - link in discord.
It has a few new systems like research and expeditions. Universes are a thing sort of but they are now realms which play in parallal to the first realm and you can move some unique stuff between them so new realms start by getting support from older ones then later they send stuff to the older ones allowing progression in them.