Slightly off topic: But what is the point of the Slideshow feature in DarkTable? Perhaps I lack imagination, but I cannot think of a single case where it would not be faster and better to export the pictures from Darktable as e.g. JPEGs and run a slideshow on them. First of all, you do not need to use your machine for photo editing for the presentation. Secondly, your pictures will be pre-rendered, avoiding problems like in the parent post. Thirdly, your slideshow will look the same, all the time. With Darktable you might encounter bugs in the rendition or you might have deliberately or accidentaly altered the edit of one or more pictures.