Gif animation and responsive image styles are not working
There's now imagemagick for Drupal 8. I've been using it with D8 responsive image styles and it works well, the gif animation stays intact. 

You'll need to have imagemagick installed on your server and will need the path to the convert binary as well. Typically it's usr/bin or for example with MAMP, it's /Applications/MAMP/Library/bin/