How do I update Godot4 mesh normals during runtime by writing into the buffer directly?

Question

I'm working on a procedural planet generator. My implementation is running a compute shader that calculates vertice positions based on noise algorithms and writing the vertex data directly into the vertex buffer using the ArrayMeshes SurfaceUpdateVertexRegion() method.

However, I can't figure out how to do the same with the updated normals. There doesn't seem to be a dedicated method for this, all I found is SurfaceUpdateAttributeRegion(), but every attempt at using that so far failed, to the point where I think that this is might be something totally different (contextually).

I either get errors that my planet mesh does not have an attribute buffer at all (which is strange since I do initialize the mesh with a normals array), or I get errors that I write too much into the buffer (the amount of bytes that exceed the buffer are the total amount of bytes I write, so basically it assumes the buffer is 0 in size.

This is the syntax for the method updating the vertices, which works perfectly fine:

PlanetMesh.SurfaceUpdateVertexRegion(0, 0, Rd.BufferGetData(VertexBuffer));

0 being the surface id (there is only 1) and 0 being the offset (no offset).

I would really appreciate any and all help or pointers how I can get this done.

I tried using the SurfaceUpdateAttributeRegion(), assuming normals would be part of "attributes", but errors messages make me doubt it by now.

A rendering server method which I forgot the name of also implied that the normals are directly stored inside the vertex buffer, but that would leave me even more clueless in how to update them specifically.

More or less unrelated planet image