Did you mean the song artwork?
As it looks like, Playlist Artwork no longer displays (at least on MacOS) on imported v5 library, regardless if it is an smart or regular playlist.
Only way to restore it is via change artwork, which is quite annoying if you have couple hundred playlists and you are used to have separate "cover images" on them.
Publicação fechada para comentários.
Did you mean the song artwork?
No, as title says, playlist artwork.
Can you clarify -- do you mean the artwork for songs within the playlist? I'm not sure if you are meaning a specific art file representing the playlist.
I mean actual playlist one.
Rekordbox 6.0.0: 
If you look closely, it recognizes that Artwork is there (change/delete artwork option is active and present), but it does not display it.
Rekordbox 5.8.5

Ah, okay - thank you. Does this happen with all playlists you had in rb5, and is it a problem with new playlists created in rb6?
All the images, were 500x500px, jpg less than 200KB, in case it does matter.
New playlists work fine, only imported/migrated from 5.8.5 seem to have the issue,
For new playlists it works fine, when you add new artwork and also, "change artwork" for affected ones, seems to fix it as well.
Only trouble is that I have hell of a lot of those playlists... :D
Thanks - I'll pass this on to our rekordbox team to investigate.
Thank you @Pulse
Check your email or go here to see the ticket I've just added you to.
Yes, saw that and replied.
Awesome - will close this topic to refer communication to the ticket. Thanks.