Very cool... looks like a bit of work went into that, might I ask what your future plans are for this? Do you plan to just leave it as is for the community to play with or continue to work on it and improve it?
Just tried it out.. my poor GPU... the lighting looks pretty awesome... the textures on the other hand... but how the hell would you do textures on that sort of proceedurally generated terrain? How would you get things to match up on those proceedurally generated triangles.. hard stuff to do well, 3D textures maybe? I have no idea.... any plans to have some graphics options to hurt my GPU a little less and give up some of the fancy lighting, for those of us who don't have awesome GPUs?
You mention using marching cubes.. have you looked into dual contouring? This page describes it
https://www.boristhebrave.com/2018/04/15/dual-contouring-tutorial/
but in a very mathy way. The basics of connecting vertices up is quite simple, look for sign changes along cell edges, connect up the vertices in the 4 cells surrounding the edge to make two triangles. That's it, no complex lookup tables, etc. However, the hard part is placing the vertices, that's where all those gradients etc. come in, but you could do something as simple as picking the average point of all the edge zero crossing points on a cell. Or something as fancy as they describe in the link above. However, I believe there are some issues with non-manifold meshes in some situations, but they aren't too often or sever, and on average I think the mesh looks better, fewer small triangles etc. and the algorithim is super simple, if you don't get into the complex vertex placement involving gradients, which I have found very tricky in practice.