We have added metainfo file to Kodi: xbmc/xbmc#20142 but appstream-generator still complaints no-metainfo: https://appstream.debian.org/sid/main/issues/kodi.html Also, I don't see what causes ancient-metadata warning.

The prebuilt Kodi package is here: https://packages.debian.org/sid/amd64/kodi/download

And big thanks from Kodi team in advance! :)