Dropbox publishes its Linux client for x86_64 only. box64 lets the aarch64 dropbox package run that client, and it has to be published before dropbox can build for aarch64. Pinned past v0.4.5-1 because that release crashes in its glib wrapper when Dropbox starts its tray icon. It ships without a binfmt handler so it does not compete with qemu-user-static-binfmt.