In English the plural of duo is duos. However, I am not sure in Spanish.
I looked in the DRAE that is the most famous dictionary in Spanish and I did not find the plural. Then, I am not sure if duos in Spanish is
Google and linguee.es translate duos to dúos.
I forgot to say that I believe that this is an important question because Wikipedia says "Los Dúo is a studio album released by Juan Gabriel on February 10, 2015."
Then, it seems that the company of the famous Mexican singer Juan Gabriel made a big mistake using for plural
dúo instead of
Thanks for your help!