Minecraft Alphernate [The latest!]: CurseForge | Modrinth | MultiMC
(I highly recommend you use ATLauncher as that can import profiles from all three!)

What it is:

Alphernate is a modpack for Minecraft 1.20.1 that aims to propose the idea of what Minecraft could have been had it gone down a different path during its alpha phase. An alternate universe Alpha Minecraft, hence the name.
Here's a trailer to get a small idea of what to expect:

The game is a lot like that, but also has enemies and cave exploring and mining and farming and flowing water and dynamic lighting and a huge (huge) randomly generated world map. AND it has music by C418!

News:

Minecraft is still in alpha, but is rapidly nearing beta. I've only got one more feature to add; multiplayer support.
I'm renaming the old version of the game "Minecraft Classic", and will be slowly phasing it out.
I won't remove it, though. Just hide it.

The main branch of the game is currently called "Minecraft Alpha", and is under heavy development. It can be a bit unstable at times, so don't get too attached to your save files yet.