Flatpak app wont run (Locale not supported by C library)

Tried to run gromit-mpx installing via flatpak , but didnt work.
I got this message from terminal:

process:2): Gtk-WARNING **: 15:53:50.630: Locale not supported by C library.
Using the fallback 'C' locale
(gromit-mpx:2): Gtk-WARNING **: 15:53:50.630: cannot open display:

any alternative to a screen writer app or a way to solve that ?

What desktop is this?

What does flatpak run --command=locale net.christianbeier.Gromit-MPX output?

locale: Cannot set LC_ALL to default locale: No such file or directory

i dont know what these means

Have you installed both glibc-langpack-en and glibc-langpack-pt?

no, unless flatpak installed, how to verify and install that on silverblue ?
that is what is causing the problem ?

should i rpm-ostree these ?

This locale issue probably isn’t fatal, but you can fix it with:

flatpak config --set languages 'en;pt'
flatpak update

Flatpak only installs locale subsets for the language(s) you’re using, but this seems to be broken for mixed locales: [Bug]: not all languages recognised with mixed locale and thus not used for Locale extensions · Issue #5497 · flatpak/flatpak · GitHub

This is the real problem. It’s supposed to work using XWayland, and it does at least run here in GNOME. I couldn’t get it to actually do anything, but I didn’t try very hard.

There’s a report of it failing similarly on sway:

i see and thanks for your support, so do you know any other screen annotation app that could run under wayland ?

If you’re using GNOME, my first thought would be an extension, but the only one I see on extensions.gnome.org hasn’t been updated in a while: Draw On You Screen - GNOME Shell Extensions

There’s an updated fork, but it hasn’t passed review for inclusion on the website: GitHub - zhrexl/DrawOnYourScreen2