Context is Key
As opposed to other more tactical game systems a lot is up for Storyteller and Player interpretation in V20. The system rules are there, but less strictly defined than you might be used to.
The Protean Earth Meld power is specifically about melding into dirt. Stone won’t work and a wood floor will block you. So you might find more than a few Gangrel favoring hovels with dirt floors.
Koldunic Sorcery is about mastery over nature. So here I would call that any ground type out in nature is fine whether that’s an open meadow or an all-stone cliff. However it’s not going to work (or at least be hindered) trying to do this in a large city.
In contrast to both of these, as an example, the Necromancy ritual Din of the Dammed has you draw a line of ashes on the ground to block sound. This will work on any ground (stone-to-dirt, city-to-nature) so long as you can draw the line unbroken on the terrain.