Greasy Fork

It seems not working for me...
Maybe your script work only if i am connected?

I have edited your script to set the auto translation for "French":
let menuTitle = "Traduire automatiquement";
let keepLanguage = ["English", "French"];
Maybe i do a mistake, because i don't see change.

Waterfox / greasemonkey 3.xx

The language name for keepLanguage must also be based on whichever your YouTube language setting is.

For English (US) language, the language name for French is "French". But if the language is French, the language name for French must be "Français".

Hmm...
I do , as you said:
let keepLanguage = ["Français"];

But i don't see in the translate option,
the Français label in first in the list.

And the :
let removeOtherLanguages = true;
don't remove the others Language label in the list.

What i need:
Just "Anglais" and "Francais" in the options of translation.

If i understand well it's the purpose of your script,

I am a little bit confuse:
My Youtube interface seems in French.

Please be aware that, YouTube's Auto-translate (if YouTube UI is in English) or Traduire automatiquement (if YouTube UI is in French) menu item will not be shown (by YouTube) if the subtitle is not yet active. So, the subtitle must already been activated before opening the subtitle menu.

The minimum settings exclusively for French subtitle on French YouTube UI are these: (IOTW, do nothing for other YouTube UI language)

let menuTitle    = "Traduire automatiquement";
let keepLanguage = "Français";

If English subtitle is preferred when YouTube is in English, and French subtitle is preferred when YouTube is in French, then then settings should be like below.

let menuTitle    = ["Auto-translate", "Traduire automatiquement"];
let keepLanguage = ["English", "Français"];

Ok, that's work!
Thanks for your time and this script....

I use:
let menuTitle = ["Auto-translate", "Traduire automatiquement"];
let keepLanguage = ["English", "Français"];