Uses lessons from Geometry Nodes from Scratch - Blender Studio to make a tileable scattering of rocks on an XY surface (ground displacement not included). Can easily be exported to glTF using Apply Modifiers option in Blender.

For those who examine how the modifier works, please let me know if anything about my node tree routing / naming confuses you.  It would be nice to have another set of eyes pointing out inaccuracies and better layouts.