i’ve never seen it explicitly stated but it is assumed
we know for a fact that Tarrlok, Tenzin, and the Fire Nation rep are benders. (we see the FN rep bend in the Republic City game.) it’s assumed that the other two are benders as well bcs when Tarrlok is addressing them wrt Amon and the Equalists fighting the benders, he says that once Amon is done with the Traids, he’ll come for other benders — he’ll come for “us”.
he could have just meant “us benders”, but since he was addressing the other council members, it made it seem like they were benders also.