Discard White Stone of Ancients to activate effect
Yes you can use the effect in the End Phase if you send White Stone of Ancients (WSoA) to the Graveyard by some means throughout your turn.

In your question you mention Dragon Ravine

Once per turn: You can discard 1 card, then activate 1 of these effects;
● Add 1 Level 4 or lower &quot;Dragunity&quot; monster from your Deck to your hand.
● Send 1 Dragon monster from your Deck to the GY.

As discarding a card implicitly sends it to the Graveyard you gain use the effect of WSoA if you discard it for Dragon Ravine's cost, or if you send it to the Graveyard as part of its effect.
Other means of getting WSoA out of your hand to use it's effect in the End Phase could be a card like Cards of Consonance

Discard 1 Dragon Tuner with 1000 or less ATK; draw 2 cards.

or you can summon it and link summon into Linkuriboh.