network-auth.com is used by Motel 6 locations with their charged-for wifi . There is a long-standing bug that authentication cannot be accomplished with Linux on the user's computer. A work-around with a dual-boot machine is to boot up in Windows, go through the authentication dance, then reboot with Linux and the authentication will work for the life of the authenticator (24 hours).
I called their connection support number one time, and after half an hour or so of work they were able to make the authenticator work. But after it expired it was back to the same problem as before.