I installed Fedora 40 awhile back but i did not know it didn’t come with multimedia codecs. That means no YouTube or any other multimedia videos. This is because they only ship free software, so no propietary packages. After some research, I came up with the following steps, and it worked, so give it a try. I have now updated to Fedora 42 and i continue to have no problems, but your experience may​ differ.

Disable rawhide repo if enabled

dnf config-manager --set-disabled rpmfusion-free-rawhide

Enable rpmfusion repo

dnf config-manager --set-enabled rpmfusion-free

Refresh repos

dnf update --refresh

Install codecs

dnf install @multimedia @sound-and-video ffmpeg-libs gstreamer1-plugins-{bad-*,good-*,base} gstreamer1-plugin-openh264 gstreamer1-libav lame* --allowerasing

---

Further reading

RPM fusion docs docs

Official docs for multimedia install Fedora Docs

Easy install of third party packages Fedy