If the article uses images/videos/GIFs with captions as the main medium, those images should not be presented as a slideshow (e.g.: travel blogs that show many photos with captions, step-by-step crafting guides, cooking recipes, etc.). Use images with captions (or even plain paragraph text) following one another. It is indeed a gallery, but should not be shown with a slideshow.
https://instantview.telegram.org/checklist#6-4-galleries-and-slideshows