Is there such a thing as vertex animation in world-space?

Every tutorial I’ve found on making material-based vertex animation uses some form of UVs. Is there a way to deform verts with a noise in world-space, so UV seams don’t tear?

Yes, use the material system’s “World Position Offset” input. This is a worldspace 3D offset that is applied to each vertex of a mesh. (Most material inputs contribute to a pixel shader for the material, but this one contributes to a vertex shader). See