I double-check the flatpak install, and it seems that I had installed the package from Fedora Flatpaks instead of Flathub. So I installed it from Flathub, and it reads CR3 files. My bad.
Nevertheless, thank you for your help @paperdigits and @darix.
I double-check the flatpak install, and it seems that I had installed the package from Fedora Flatpaks instead of Flathub. So I installed it from Flathub, and it reads CR3 files. My bad.
Nevertheless, thank you for your help @paperdigits and @darix.