Comic book files of the .cbz format don't want to open in Okular in Neon dev-unstable or user now, the same has been confirmed in opensuse tumbleweed.
I'm testing with file http://embra.edinburghlinux.co.uk/~jr/tmp/comic.cbz The same file works fine in Peruse. Looking in Dolphin it says the file is a Zip archive, could there be a problem with the mimetype recognition? https://bugs.kde.org/show_bug.cgi?id=374133 Jonathan