I've just found out about what I think is the first French translation of Sextus Empiricus's Against the Ethicists:
Sextus Empiricus, Contre les moralistes (Adv. Math. XI). Traduit, présenté et annoté par Olivier D'Jeranian. Manucius: 2015.
I cannot recommend this translation because I haven't seen it yet and I don't know the translator, but you can find more information here.