To me it seems that the "Recent" folder is missing special attributes (whatever they may be).
In German, when the file dialogue is shown, it is "Zuletzt verwendete Dokumente" (recently used documents) and has a special icon.
However, when running a Samba PDC, it only is "Recent", with no special icon.
Attaching two screenshots: nodomain.jpg is showing the icon when not using a Samba PDC, but a standalone machine. domain.jpg is showing the icon when using Samba.
Created attachment 1638 [details]
the icon when not using a Samba PDC
Created attachment 1639 [details]
the icon when using Samba
the "special folder" attribut (r/o on folders) is supported if you turn on xattrs on the filesystem and set "store dos atributes = yes" and turn "map read only = no". Not too intuitive but that should do the job nowadays.