This isn't new, the 1.9M were already up. It was one of my favorites and its in a list I keep of "High Quality Collections of Digitized Art and Archival Finds" (here: https://simonsarris.com/art-collections)

What's truly new here is a detailed search function that works FAR better than the old one, which would sometimes have a warning/apology box that it didn't quite work!