i think there is a mix up. fiber doesn’t change anything regarding threejs, there are no new or altered objects etc, it merely reflects the threejs that you have installed as is.
a long while ago threejs deleted PlaneBufferGeometry (along with all other buffer geometries, as well as THREE.Face3) and now there is only PlaneGeometry, you do not have access to faces no more and dealing with attributes is a bit more complicated. what you’re looking for is essentially how to upgrade an old threejs example to modern threejs, i think if you re-word that you would get more attention.
ps, this thread describes the migration THREE.Geometry will be removed from core with r125