You could try using Album Art Downloader
Select File > New > File Browser...
and scan your music folders in manageable chunks.
This will show if albums have any album art, and whether it is embedded or external.
It checks for embedded artwork first, so if the Artwork Status
shows a track file name, that track contains embedded artwork.
First album has no artwork.
Second album has external artwork only.
Third album has embedded artwork (or both).
It will require your music to be well tagged or well organised so it can determine which tracks make up an album.
Bee excellent to each other...