How do I recruit Germanic Nobles as the Langobards?

I've hovered every tech and every building and can't find it. According to this website: https://www.honga.net/totalwar/attila/unit.php?l=en&v=attila&f=att_fact_alamanni&u=att_ger_germanic_nobles

It says if I unlock the Defined Military Obligation military tech it will be available, but for me that only unlocks Germanic Spearmen, not Germanic Nobles. The next tech, Army Drills, says it unlocks Redoubtable Cheifton to replace Germanic Nobles, but I can't even figure out how to get Germanic Nobles in the first place.