Hi there, if you still need, I was able to get this to work on my end by adapting the code in this thread. I included Spanish also just to see how adding more languages would go. For your survey, first head to the General section of the survey's Look & Feel and add the below to the survey's Header:





Then, head over to the Translations section of the Builder and add "French (Canada)" as a language.
Finally, create a Text Entry question and add the below to the question's JavaScript:
Qualtrics.SurveyEngine.addOnload(function()
{
/*Place your JavaScript here to run when the page loads*/

if ("${e://Field/Q_Language}" == "EN") {
lang = "default";
} 

if ("${e://Field/Q_Language}" == "ES-ES") {
lang = "es";
} 

if ("${e://Field/Q_Language}" == "FR-CA") {
lang = "fr";
} 


});

Qualtrics.SurveyEngine.addOnReady(function()
{
jQuery("#"+this.questionId+" .InputText").flatpickr({
"locale": lang,
dateFormat: "Y-m-d",
maxDate: "today"
  });

});

https://community.qualtrics.com/XMcommunity/discussion/comment/52094#Comment_52094 You don't need if statements to set the variable lang.

"${e://Field/Q_Language)".substr(0,2).toLowerCase();