Many in the Legion were from eastern European countries overrun by the Russians after WW II. Others were, as mentioned, Spanish or Italian or from the Balkans etc. Of about 15,000 soldiers that passed through DBP on the French side, slightly under 4,000 were in the Foreign Legion. Of these, no more than half were German. Also, the average age in the Legion at the time of the battle was 23 years. Many of these men had been boys during WW II.
In addition to Frenchmen and the Legion and Vietnamese filling out units (a quarter to half their number in many cases), the French also employed colonial troops from their other possession. Moroccans and Algerians fought at DBP on the French side. There were about 2500 North Africans in the DBP fight. From among the Vietnamese, about that many were T'ai tribesmen, a mountain tribe local to nearby areas that resisted the Viet Minh.
T'ai, other Vietnamese, Germans, other Foreign Legion, North Africans, and mainland Frenchmen (especially from elite formations like the paras) all contributed sizeable contingents to the DBP force.