How do I add codecs in Tumbleweed? I have added pacman; but it doesn’t want to add most of the codecs in this repository such as ffmpeg.
It is not quite clear what you did. When you only added the Packman repository to your list of repositories, then that is of course insufficient. You must also make use of it.
Either YaST > Software > Software Management then Repositiries from the View menu. Then select the Packman repo from the list at left. At right there is a list of packages, above it is a line saying something like “Switch system packages …”. Click on it and proceed with installation.
zypper dup --from <some identification of your Packman repo>