Gtk-message "Locale not supported by C library"

[Ricky-Tigg]

$ flatpak info -o --show-runtime app.drey.Dialect
flathub org.gnome.Platform/x86_64/48

Hello. Weblate, the localization platform chosen by this project, is shows that the locale that matches the one on the Linux distribution I use is translated. Nevertheless as per this message, that locale is not supported by the C library this application as Flatpak-formatted obviously relies on. As a consequence, source strings, despite being translated are not exhibited in the GUI.

$ flatpak run app.drey.Dialect
(process:2): Gtk-WARNING **: 13:57:34.270: Locale not supported by C library.
 Using the fallback 'C' locale