Well, the problem is that both systemsettings and systemsettings5 are called “Configure Desktop” in Leap.
The application menu then hides one of the duplicate entries.
We always had/have a patch in openSUSE to rename KDE4’s systemsettings to “Configure Desktop”, and we have the same for systemsettings5.
Since the switch to Plasma5 as default, KDE4’s systemsettings is being renamed to “Configure KDE4 Applications”.
But, this patch is only being applied for openSUSE 13.2 and higher.
And when Leap was introduced (long after the switch to Plasma5 was made), it was announced as 13.15 actually (in OBS at least) as it is based on SLE12.
In this case this was overlooked, so the wrong patch is applied in Leap and KDE4’s systemsettings is still called “Configure Desktop” as well.
I submitted a fix to the devel repo already, so this should be ok in the next Plasma update for Leap.
Unfortunately, there’s still one problem left then:
openSUSE’s translation team (which I am not part of) neglected to translate this at all since years.
So for other languages, both still will be called “System Settings” (in the upstream translation), as is the case in Tumbleweed.
I hope we can get this fixed as well though.
For now, a workaround would be to create a menu entry for systemsettings5 yourself, or uninstall kdebase4-workspace-addons (which contains the KDE4 systemsettings) if you don’t want/need it.
I did a live upgrade from 13.2 to Leap and although I had plasma 5 on 13.2 it seams I still have a few kde4 apps running around any idea how to get rid of them and use plasma 5 apps
Other than systemsettings/systemsettings5, there shouldn’t be a problem.
Not all applications are ported to KF5 yet, so this is even to be expected.
You can perfectly run KDE4 applications in Plasma5 (KDE even takes care that they are integrated), as you can run them in any other desktop environment, or even MacOS X and Windows.