I've had a fair amount of #fun with Luanti (Minetest). It's an open source game similar to Minecraft. The only downside is if you are expecting a nearly 1:1 recreation of Minecraft with the same features you'll have to do a bit of modding.

That said the game has a really rich modding scene and from what I can recall the modding process was quite easy.

Starbound is fairly close to Terraria, but in space.

Luanti maybe

I know that Factorio started as a minecraft mod. But that completly stands it's own ground. I would have never called it a clone thou

https://veloren.net/ - free and open source voxel based with RPG elements

@Pamasich@kbin.earth Since you mentioned Terraria and Minecraft, I'll put Core Keeper on the table too! :) It's fantastic, especially Co-op

There is Eco global survival, but i havent played it

There is also Forager which i think counts

Gelatine probably doesnt fit the requirements for a minecraft "clone"

Raft, maybe kinda?

clonk but it's older than minecraft