Move over Cube World, there's a new open source voxel RPG in town under development called Veloren and it supports Linux too so there's a bonus point for you.
Inspired by many games like Cube World, Legend of Zelda: Breath of the Wild, Dwarf Fortress and Minecraft it's currently under heavy development, thanks to user email tips I've been keeping a close eye on this one. I don't want to get your hopes up too high but it's already coming along well and shows a ridiculous amount of promise.
Their regular progress reports on the official site blog have been a thoroughly interesting read. So many interesting features and world generation updates coming along for it. You can see some gameplay in their recent raw video below:
As you can see, it's a little rough around the edges in many ways but already pretty playable. Once there's a bit more to do, it could be good for a few hours of exploration.