Delta Huntail doesn't learn Draco Meteor from the dragon move tutor
Are you sure it's supposed to?
All Dragon types (excluding Mega evolutions) are supposed to learn Draco Meteor by move tutor. This includes most dragon-type Delta Pokemon - Delta Charizard, Avalugg, Sceptile, Pidgeot, and Electivire. The sole exceptions are all members of the Delta Clamperl line.