I received the error: Requested download is not authorized for use with this tracker.
When opening the link at: http://cdimages.ubuntu.com/lubuntu/releases/xenial/release/lubuntu-16.04-alternate-amd64.iso.torrent
In transmission. I was able to open the link to and successfully download the desktop iso from: http://cdimage.ubuntu.com/lubuntu/releases/yakkety/release/lubuntu-16.10-desktop-amd64.iso.torrent
Maybe the alternate installer iso is somehow disabled on the tracker? I was able to download the installer via the hhtp link but it was very slow (~300kbps).