Which reef clan did Jake's family join before Fire and Ash?

Jake’s family joined the Metkayina reef clan before the events of Avatar: Fire and Ash.

In Avatar: The Way of Water, Jake Sully and Neytiri move their family away from the forest home of the Omatikaya after the RDA returns to Pandora and begins targeting Jake. They seek refuge with the Metkayina, a reef-dwelling Na’vi clan led by Tonowari and Ronal. The Metkayina live around the coastal village of Awa’atlu and have adapted their bodies, customs, and skills to life in the ocean.

The Sully children initially struggle to fit in. Lo'ak, Kiri, Tuk, and Neteyam must learn reef traditions, underwater breathing techniques, and the Metkayina way of interacting with marine life. Lo'ak’s friendship with Tsireya and his bond with the Tulkun Payakan become especially important. Jake and Neytiri remain Omatikaya by heritage, but the family becomes closely connected to the Metkayina community.

The alternatives refer to different groups. The Omatikaya are Jake and Neytiri’s original forest clan, while the Olangi are a Na’vi clan seen in the first Avatar film. The Mangkwan are associated with the Ash People in Fire and Ash, not the reef community that sheltered the Sullys.