Hi,
When I set the region to 'Guadeloupe - français (fr_GP)' in 'Formats', I get the following warnings in the terminal :

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = "fr",
        LC_ALL = (unset),
        LANG = "fr_GP.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory

In 'Translations' > 'Preferred languages', French is set.

When I set the region back to 'France - français (fr_FR), the warnings don't appear anymore.

Reproducible: Always