In the .glb and .gltf export settings, I couldn't find a setting to disable geometry triangulation. How to disable geometry triangulation in .glb and .gltf files?
Do you mean that you don't want the mesh to be triangulated?
If so,
Currently GLTF format has a lot of limitations, one of them being this. Triangulation cannot be disabled, because all objects will be exported with faces converted to triangles, if you still want to have object as non triangulated, I'd suggest you use a different format like .obj
For detailed reasoning, you can refer to this: Why GLTF Why!!
If you ae having difficulty understanding the comment in the link I shared then maybe try asking AI to help you understand.