The server can do this with the Content-Disposition header. The `download` attribute just lets you trigger downloads (optionally with a filename) for URLs that otherwise wouldn't be downloaded.
Even IE 11 has a way to do this (non-standard, of course, but it does have a way to do it :-). Edge supports the standard way.
As I noted in a different post, though, support for the download attribute has already landed in Webkit Nightly for macOS, and is apparently being worked on for iOS.