there is also another paragraph that says that the cover is not desirable (optional), in articles with one image/gif/video...
Type of issue
IV page is missing essential content
Reported
Mar 6, 2019
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It is obligatory to use a cover image:
https://instantview.telegram.org/checklist#6-2-2-cover-images
If the image is present on the page and described in the source as “featured-img”, “cover”, “lead_img”, “main_image”, etc.