Can not change language

[fs1995]

Version, Operative system
Version 0.99.55
Linux Mint 21.1 (Flatpak and AppImage)
Pop!_OS 22.04 (Flatpak)
Fedora Kinoite 38 (Flatpak and AppImage)

Describe the bug
CherryTree is only displayed in English, regardless of language selected. Even when selected "System Default", and my system language is not English, CherryTree is in English.

To Reproduce
Flatpak and AppImage versions seem to be stuck in English.

[fs1995]

Here is the error I get when launching:

[silver@Silver-5580 Downloads]$ ./CherryTree-0.99.55-x86_64.appimage 
** Message: 16:56:28.874: Language overwrite = de (localedir = /usr/share/locale)

(process:3831): Gtk-WARNING **: 16:56:28.944: Locale not supported by C library.
        Using the fallback 'C' locale.

[giuspen]

I will try to solve before the next release, I'm busy at the moment completing the biggest feature that will land in 0.99.56 (support for a new multifile storage)

[giuspen]

I can see that the AppImage is not working but the flatpak seems to be working for me.
What I get is: ** Message: 23:51:16.552: Language overwrite = it (localedir = /app/share/locale)
Can you show me also what you get from the flatpak too?

[fs1995]

I have live booted Ubuntu 23.04 to do the following testing:

I installed flatpak normally (as system), and CherryTree language does not change from English. I get the same error on launch:

** Message: 00:44:48.240: Language overwrite = de (localedir = /app/share/locale)
 
(process:2): Gtk-WARNING **: 00:44:48.243: Locale not supported by C library.
	Using the fallback 'C' locale.

I installed flatpak again as user (with the --user flag), and I can now change the language! I selected several randomly, and seems to all work.

AppImage still can not change language.

[giuspen]

In upcoming 0.99.56 this problem will been fixed for both flatpak (with no need of --user) and appimage