Like I said earlier the file format .gif works just fine no matter the browser, the problem lies in animated .webp files for which Safari support has been added in ios 14 and many websites are now switching to. Unfortunately the fotos app didn't get the same treatment...
TuHnix
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It hasn‘t just been a problem with the last four updates its been a problem since at least 14.0 public beta 2 (don‘t know about public beta 1). It’s not even a bug just a missing feature of playing animated webp images in the fotos app.
In my opinion it should really just convert them into gifs when downloading them...