For now Amarok doesn’t really have one,it may in the future.
I personally am not holding my breath for them to do so.(they consider it a toy)
If you really need a music player with an equalizer, my recommendation is Audacious. Audacious is a very simple player with an equalizer & I find it quite intuitive. It’s in the Packman repos.
Welcome to OpenSuse & its forum.
It’s really a combination of packages that can likely be sorted by either waiting to see if the online updates eventually patches the current versions of software that oh by the way makes the eq work (slowest method), or by carefully selecting the repositories that will bring a later revision of amarok, libphonon, phonon-backend-xine, libffmpeg0 (likely that’s packman), libxine1 stuff.
The current debian testing, debian-multimedia.org combination on debian includes a working eq in amarok, which I’ve been enjoying as it works nicely. A full gui of it is within amarok preferences and a preset list is included in the amarok menu drop-down so I don’t need to open the preferences to use it.
As you’ve already posted (and been reminded) about some of the packages to look for in the repos, you may experiment away with adding repos and upgrading certain packages. Note that upgraded kde libraries might be necessary for things to work properly. And that you will be getting into the realm of using packages that are not officially supported/bug-fixed by online-updates and will be dependent upon keeping the added repos active and regularly upgrading with them in order to receive any fixed, which also come along with new features and new bugs!
Safer will be to do without the eq unless officially brought in by the update service using the updates repo (and of course oss and non-oss, and packman if you use it for multimedia-packman folks may at some point want to patch in the required stuff if there is a calling for it and it isn’t that much required. Or not because, hey, it does look like more than a simple player upgrade.)
It depends upon whether you want to use a safe strategy or go more on your own and track some of those next opensuse development repos. I used both methods on opensuse in the past and can tell you I was happiest sticking with the officially supported (well, except for packman) safe method. Too much watching tons of updates and occasional dependency tweaking on a manual basis for my taste.