https://vgmdb.net/album/74611

Yes, I know it's a BD pack-in. Yes, I know it's expensive.

A man can dream. :v

It seems to be available on torrent here (https://nyaa.si/view/1030821). I don't have checked if it's good yet.

EDIT : You can find in on HNA (http://hikarinoakariost.info/darling-in-the-franxx-original-soundtrack-vol-1/) too, enjoy!