Could it be that you’re not on F41? The mentioned command has the dnf5 syntax, provided with F41, while the command line error above seems to be issued by dnf4, used by F40 and earlier versions.
However, dnf repolist might indicate that the fedora-cisco-openh264 is already active. If not, check the usage for dnf4 (see man dnf config-manager).
I think I see a typo there.
It should be sudo dnf config-manager --setopt fedora-cisco-openh264.enabled=1 if you are on fedora 40 using dnf4 and sudo dnf config-manager setopt fedora-cisco-openh264.enabled=1 if on f41 and using dnf5 (the default for f41). The switch from dnf4 to dnf5 changed the mandatory syntax.
Notice the prompt you got within the error message
I edited your post to add the preformatted text tags to that output so it appears here exactly as you saw it on screen. Please use those tags (available with the </> button on the toolbar) when copying text and pasting it here. Doing so keeps everything so it is much more readable.
dnf5 config-manager some-missing-subcommand
Unknown argument "some-missing-subcommand" for command "config-manager". Add "--help" for more information about the arguments.
In dnf4 the command as given is invalid. --setopt would be correct. setopt is not correct for dnf4 but is for dnf5.
(Edited this post and my post above to correct my error)
dnf5 config-manager setopt repoid1.enabled=1 repoid2.enabled=0
Sets override to enable repository identified by repoid1 and disable repository identified by repoid2.
Perhaps it should be added that the configuration changes will be written in a new override file in /etc/dnf/repos.override.d/99-config_manager.repo and the original files /etc/yum.repos.d will be untuched.