Meanwhile I found this bug report that seems to be related to your issue: https://bugs.kde.org/show_bug.cgi?id=344519
In short, KDE4 might load KF5 plugins by mistake and vice-versa.
Still, to “fix” your issue, we’d need to know which plugin causes the crash.
The debug output should tell.
This will not help then though:
Does kded start on login if you rename the folder /usr/share/kde4/services/kded/ and run “kbuildsycoca4 --noincremental”?
But deleting/renaming /usr/share/kservices5/kded/ should.
Or uninstall all (Plasma5, KF5) packages that install files into that directory.
You can get a list with:
Sorry about the massive delay on this; I didn’t want to shut my computer down until now because I was concerned about it not starting and me not having the time until now to do anything about it.
Anyway, I renamed the services folder like you mentioned, ran kbuildsyscoca, and now I have two copies of every service, but KDED is running and everything finally seems to be correct.
Ok, so apparently kded4 does indeed load a kded5 plugin.
This is a workaround then, but it still would be preferable to find out what exactly causes the crash I think.
Can you rename the folder back and post the output of "rpm -qf /usr/share/kservices5/kded/*? Maybe something obvious is installed that shouldn’t be…