Note to myself, but maybe you found this article via search engine... 🙂
Symptome: You are trying to post-process a Canon CR3 RAW image file with Darktable, but it doesn't show any CR3 files.
Reason: Darktable uses LibRaw for reading CR3 files, which in turn uses exiv2. New file formats are not compiled into Fedora's exiv2 though, presumably for licensing or patent reasons (see this bug report, tl;dr).
Solution: Uninstall Fedora's Darktable version (either via dnf remove darktable or flatpak uninstall darktable), and install the flathub version via flatpak install darktable.
If you used the dnf version, you can copy the ~/.config/darktable directory to ~/.var/app/org.darktable.Darktable/darktable to keep your Darktable configuration.