• steps to reproduce:
  Open any folder in Dolphin.

• expected result:
  The folder contents should show.

• actual result:
  Instead, for some folders, I get a message that says “Unable to create io-slave. klauncher said: Could not find the '/usr/lib/qt/plugins/kf5/kio/file.so' plugin.” and “Folder is empty”, but only for some folders.

I know you did some stuff with kio recently, so I assume this issue has to be related with the latest changes made to the repository.