Several points that make me think that Shanks is the Yonko who owns Elbaf’s island.
In this theory, I will claim the points that make me think that the protector of the island of Elbaf is currently the Yonko Shanks.
I – New World Territories Functioning
Elbaf is the island of the Giants species in the New World.
The islands of the New World we saw till now are:
– Fish-Man Island, under the protection of the Straw Hat Pirates (previously under the protection of Big Mom and before that under the protection of Whitebeard).
– Punk Hazard, under the protection of Caesar Clown, linked with 2 Yonkos and with Doflamingo (previously it was owned by the World Government).
– Dressrosa was under the protection of Doflamingo. Now is owned by the World Government.
– Zou, independent island but led by Nekomamushi and Inuarashi, former pirates of Whitebeard and Roger.
– Totto Land, under the protection of Big Mom.
– Wano, controlled by Kaido who took it by force.
In the New World, most of the territories are owned by the Yonkos. Elbaf is foreshadowed since a long time, and the Straw Hats will go there for sure.
But it’s hard to tell how this island works, who owns it. I believe the most evident Yonko candidate for this is Shanks.
II – Viking’s Thematic
So, basically it’s pretty obvious that the Giants of One Piece are inspired by the Norse barbaric explorers: the Vikings and their mythology.
Gungnir is the spear of the god Odin, chief of the Norse Pantheon.
The epithet of Shanks is “Red Haired Shanks”.
First, his inspiration comes from “Calico” Rackam Jack, famous pirate which the flag inspired Shanks flag for the Red-Haired Pirates.
But also, Shanks is inspired after Erik the Red, a Norwegian Viking.
The “classic” ship of the Viking is called a Drekar. The bow with a shape of dragon.
It’s basically what Shanks possess: the Red Force.
Also, look at the ship and the flag of the original Giants Pirates crew:
Shanks is also inspired after the god Týr, associated with law and heroïc glory in Norse Mythology
Tyr is a one-arm character who sacrificied his arm to the monstruous Wolf Fenrir.
Remember the Sea King and Shanks sacrifice?