Luanti (formerly Minetest) has a fresh small release out with v5.14 bringing a couple of gameplay tweaks and various other improvements. What is Luanti? An open source voxel game engine. You can play many different games made with it, like the popular VoxeLibre pictured below.
Pictured - VoxeLibre in Luanti
This Luanti release makes a tweak to the main menu to help prevent player confusion, removing world-related options when no world is selected. They've also made it easier to select text in the menu and game text fields, and nametags can now scale by distance to help you see who is nearby and who aren't. Some other changes to the game include an update to particles like the when you're digging, with these now shown to all players, not just you.
My favourite little change from this release is the upgrade to how the minimap works. Now it actually shows the correct tiles on top of land, like grass, so you know exactly what's around you. Small thing but looks much better.
Grass on minimap in Devtest before and after
There's also been some optimizations to how certain mapblocks are stored, plus textures should now load faster with paths being cached and more.
Lots to come in future release with some of their plans to include inventory image animations, a dark mode theme for the main menu, more accessibility settings and the list goes on.

Is it basically an alternative to Minecraft in terms of gameplay and features? It's not Java so I imagine its a different experience but I'm curious if there are established communities and such like Minecraft has?
The engine has several minecraft-clone style games, and the engine is extended with Lua, which provides about as much flexibility as the Java Edition of Minecraft. It has a decently active modding/game making community, with clones for advanced trains, technic-inspired stuff, monsters, etc. It doesn't have 1:1 featuresets, as that would be highly illegal, but it rhymes. Some things are honestly a LOT better in Luanti than in Minecraft - for example you can join any modded server and don't need to have all the mods pre-downloaded. The server sends you what you need. And yeah it has a very active discord, forums, blog, X/mastodon, youtubers, etc.