AFAIK, all the other ui.\* preference affect the Firefox UI, not websites, so it...

AFAIK, all the other ui.* preference affect the Firefox UI, not websites, so it's a misleading name. And I have already disabled web page animations in userContent.css[0], which is the correct place for modifying CSS. I shouldn't have to choose between allowing annoying UI animations and allowing fingerprinting.

[0]To disable web page animations, in Chrome/userContent.css in your Firefox profile directory:

  @namespace url(http://www.w3.org/1999/xhtml);
  *, :before, :after {
    transition: none !important;
    animation-delay: 0ms !important;
    animation-duration: 0ms !important;
  }

This also requires setting toolkit.legacyUserProfileCustomizations.stylesheets to true in about:config