Please specify which texts are untranslated here in the ticket.
The title is pretty unspecific.

I am just reporting what I am seeing in the forum. Therefore I have posted the links to the forum posts, where people reported about this.
Here another post about missing translation: https://www.limesurvey.org/forum/can-i-do-this-with-limesurvey/94151-change-the-message-displayed-when-someone-opts-out#167123
This should be a related bug: https://bugs.limesurvey.org/view.php?id=13211

I'm running 2.7.x and I see that the OptOut page text is in English, even though the URL is :

/index.php/optout/tokens/689385?langcode=fr&token=RrtGUfjgO3K0zQw

Specific texts are:

Please confirm that you want to opt out of this survey by clicking the button below.

After confirmation you won't receive any invitations or reminders for this survey anymore.

I confirm.

I've attached screen shot of the email with the French lang tag, and the on-screen opt-out message.
I also checked the fr.po file for LS 2.7.x and the above strings don't exist.

1.png (70,429 bytes)   

1.png (70,429 bytes)   

2.png (31,564 bytes)   

2.png (31,564 bytes)