As some of you may noticed, we removed the dataset card from the layout builder on 23 January 2019. This was because the gallery card supports datasets, has the option to display multiple items, has additional styling and responsiveness to mobile browsers, and has the ability to select "manual" items (instead of only being group-based). We are hoping you'll be able to get all your dataset card needs from the gallery card! However, we're interested if you think there's something we missed or some reason you really loved the dataset card we definitely want to hear from you.
Also - in case you were worried, all existing dataset cards will continue to function. We only removed the ability to create new ones.