No–all polygonal models include GeomNodes, as far as I’m aware. My understanding is that GeomNodes are simply the nodes used by the engine for the holding of geometry–whether that geometry is procedural or loaded from a model.
I believe that the manual has a section discussing procedural generation in Panda–you should find it here:
https://docs.panda3d.org/1.10/python/programming/internal-structures/procedural-generation/index
Otherwise, I think that I’ve seen some examples posted on the forum–you might find them in a search.
[edit] Come to think of it, I think that I recently saw some tools posted for the generation of simple shapes, such as your ring.
Ah, here: