No media cover art with Kodi or Volumio

My media sources (in the built-in Media Browser) do not display cover images. When browsing Volumio and Kodi media libraries, I don’t see any covers. The covers usually DO appear when actually playing the media, but never while browsing. Media are stored on a local NAS via SMB. Kodi DID display thumbnails before (a few months back probably). I also do get thumbnails with the custom Kodi Media Sensors integration from HACS, so I know the metadata is there and available.

Any tips?

Same here, but only through Nabucasa external cloud: if accessed directly from ip:8123 everything works.
Should be a bug in the Nabucasa system, but I do not know where to report it…

Not for me. Empty even via local IP.