2023-12-14. To restore animated thumbnail previews, requires inline previews to be disabled in your Youtube settings. Note: not Greasemonkey compatible.
< 脚本Restore animated thumbnail previews - youtube.com的反馈
Well in the end I have come up with something that should work against the above described change (assuming they don't make further changes to what I saw). I'm not uploading it yet since Youtube seem to have rolled back the experiment for now and it could do with a bit more refinement as by necessity it's more complex than the current hack/script. But if you experience this issue comment here on this thread and I'll upload it or else if Youtube roll it out to affect me again I'll upload it at that time.
NOTICE: Youtube seems to be trialing an experiment on some user accounts that breaks the restoration of animated thumbnails on the homepage. I have experienced it myself and had it reported by other users, but it depends on your account so you might not be affected. Also the Youtube change has been reverted in my case and other users, to be working again; which I hope will stay the case for a long time.
I had a chance to look and the change is that Youtube no longer passes in the animated thumbnail URL in affected responses and this is required to be sent by Youtube as there are random tokens included that can't be generated client side. Therefore it seems unlikely it will be possible to restore the animated thumbs if Youtube goes ahead with implementing this change in full. I'm trying to think of alternatives but it's low chance of success. This may be near the end of the road.
The search result and video pages are still working under the experiment with animated thumbs, so this script hack may work for a while longer on those pages.