Around November 2024, mine were all moved to a folder tree "Migrated Paper Docs" in my dropbox in a folder tree, as .paper files. The web UI says the folder has 84 decedents. My backup, done through the API years ago has 118, but there may be some deleted ones in there.

If I go to paper.dropbox.com, I only see six under "starred" in the left hand side (after unfolding the tree) and two in the main area. After opening another starred one, which links into dropbox, the main area now shows three.

So the migration to dropbox did mostly work for me, but whatever was left at paper.dropbox.com is messed up.