Currently, elisa appears to be reading cover.jpg files in the directory of an album, but not the covers from the following sources: - inside the metadata - in files matching regex "(artist \- )?title\.(jp(e?g|e)|png)" where artist and title are the respective values from the track metadata The latter is usually how e.g. bandcamp distributes their album cover files, along with album covers in each track's metadata.
On second look through my music collection, some bandcamp albums actually seem to use "(artist \- )?title - cover\.(jp(e?g|e)|png)", i.e. a "- cover" appended after the title.
Bandcamp albums work for me too. The other bit about the tracks metadata has already been reported and is being tracked in task T6255 (https://phabricator.kde.org/T6255)
*** This bug has been marked as a duplicate of bug 380442 ***