When an animated GIF or PNG (APNG) is uploaded, the entire file should be converted and placed inside the image tag <img src="data:image/png;base64,
Actual behavior:
When an animated GIF or PNG (APNG) is uploaded, only first frame is placed inside the image tag <img src="data:image/png;base64,, preventing animation to be used in the answer.
IMPORTANT NOTE: if the image is converted outside the Zammad into base64 and DevTools of the browser are used to inspect and paste the entire image, Zammad will process it correctly and store in the ticket or KB article.
Steps to reproduce the behavior:
Create an animation using ShareX or any other screen capturing software. Drag and drop the resulting image into the ticket or KB article.
You are correct, however, these are two different issues from the development side. One is to recognize animated PNG file (APNG extension), the other is to convert image content fully, even if it is a sequence of frames.
Zammad does support drag-and-drop for GIF files and is also allowing to drag and drop the PNG files. Files with APNG will be attached. What we discovered in the process is that on drag-and-drop Zammad only allows first frame of the sequence to be used.