Node Group
Ground Projection Modifier
Get this Node GroupProjects the Z-Axis direction a chosen object to the Z-Axis ground of the lokal object, means: the object will be positioned where the z-axis of the chosen object will hit the object's ground. This effects only the XY axis, this is kind of a reverse "Track-To" modifier.
Add this modifier to the object you want to keep on the ground chose the "projector object" in the modifier to get the Z-direction from. The objects will be rotated on it's lokal z-ground where the z-axis from rhe "projector object" hits.