Ok, I started maybe too quickly, copying a Simpli-(Corporate Style) template and trying to customize it....
I deleted all what I did to come back to the original configuration....
What surprises me: among the 11+2 templates available, all of them except Simpli-Default, Simpli-(Corporate Style), Simpli-(Landing Page), and Simpli-(Integration) support the multi-language setting I selected (English, German, and French)...
It works fine with Beez3, Simpli-Green, -Red, -Blue, -Orange, -121, -magazine style, -photography, and even Protostar....
Can you explain that?