... since a recent(?) update. Currently using TW 20180109 & Dolphin 17.12.0


It seems because the mime type is now seen as "font/ttf" and "font/otf" rather than the former "application/x-font-ttf" and "application/x-font-otf"

Adding "font/ttf" and "font/otf" to the "MimeType=" entry in "/usr/share/kservices5/fontthumbnail.desktop" restores the (Dolphin) font previews.


(I guess this may apply to other font types as well... ?)