I did a recent install with the newest ISO. I have many modules simply missing altogether. I have a desktop with Linux also so can compare the two in terms of UI. Many icons are missing from the System Settings. When I click on some I get error messages.
I get messages like:
Could not find plugin ‘GTK’ for applicatioon 'systemsettings’Library “kcm_cgc” not found.
Nothing shows up in 'Login Screen (SDDM) and it has a yellow yield sign on the icon. Also borked are webaccounts, accounts, and general settings for Instant Messaging and VOIP. KWallet I was able to reinstall.
These are known issues with the current state of KDE SC 4, many of these plugins have moved from kcmshell4 to kcmshell5.
For the GTK module: kde-gtk-config
The SDDM configuration KCM plugin is no longer available or compatible with KDE SC 4 as it has been depreciated and replaced with the KF5 branch version.
Telepathy is also now a KF5 based application as well and what used to be called webaccounts is now integrated into KF5 and kde-telepathy called kaccounts: kaccounts-integration, kaccounts-providers, telepathy-kde-accounts-kcm, libaccounts-qt4/qt5 (depending on KDE SC 4 or Plasma 5) and libaccounts-glib.
For anything else you’ll need to look for the right application to install as the KCM modules are now bundled with there parent applications.
Keep in mind that there are a couple of these kcm .desktop files included with the Netrunner Rolling ISO that are Ubuntu specific and have no parent application on the Manjaro base.