How to block YouTube’s annoying and pointless new animated ‘thumbnail previews’ of videos in the search-results.
1. Open your uBlock Origin browser ad-blocking addon.
2. Go to uBlock’s “My Filters” tab.
3. Add …
…to any blank line, either at the top or start of your Blocklist, as you prefer. This leaves preview thumbnails intact, while stopping the ‘animated GIF-like’ previews that play when you mouseover the search result.
A similar rule should work in other ad-blockers.