Does KDE provide such a utility or should I use the generic xdg-utils?
Yes, KDE read these mimeapps.list. The code is written in mimetypedata.cpp
KSharedConfig::Ptr profile = KSharedConfig::openConfig("mimeapps.list", KConfig::NoGlobals, QStandardPaths::GenericConfigLocation);
KDE would try to read them in this order
.config/kde-mimeapps.list
.config/mimeapps.list
/etc/xdg/kde-mimeapps.list
/etc/xdg/mimeapps.list
/usr/share/applications/mimeapps.list
Not having some of these files is not a problem because it depends on your KDE version and your distribution. KDE would consult whichever is found.
What is the procedure to put KDE's house in order in regard to mime types (for local user and system-wide)?
For local users, you can edit or create the files in your .config directory. Whereas, for system-wide use, you can create the ones in /etc instead.
However, most of the time there is no need to touch those files manually. You already have ~/.config/mimeapps.list created. If you want to change the application associated with any file extension just right-click -> Open With -> Other Application.... Choose your new application and tick the checkbox Remember application association for all files of type.... This would edit your ~/config/mimeapps.list for you. E.g, if you want to change PDF association to evince instead of okular, you do this and the entry
application/pdf=org.gnome.Evince.desktop;
would be added to your mimeapps.list. The application/pdf is guessed from /usr/share/mime/application/pdf.xml entry. So, feel free to learn the syntax this way or use xdg-mime instead. Here is the MIME applications associations specification
