Description of problem: Cannot play or show thumbnails of video files because digikam must be compiled with video support (QtAV) according to FAQ: https://www.digikam.org/documentation/FAQ/#thumbnail-generation-fails-on-video-files Help -> Components Information shows "Media player support: no". Version-Release number of selected component (if applicable): 5.8.0.2.fc27
Unfortunately, upstream's choice of using QtAv, a library that has non-freely redestributable dependencies (due to software patents) means fedora cannot ship it, or enable this digikam feature. *** This bug has been marked as a duplicate of bug 1415498 ***