The Plugin is called Simplygon. Not sure if Epic plans on developing their own LOD generation (the static mesh auto LOD seems to be exactly the same as with Simplygon), but as Simplygon is completely free nowadays, including royalties (which was 2% some time ago) there’s no reason not to use it.
It doesn’t work “in runtime” though (neither for skeletal nor static meshes), you generate the LODs in editor.