One other level of classification that is missing here is "Free, but requires a local phone number." Oftentimes, the operator will send you an SMS with a one-t

One other level of classification that is missing here is "Free, but requires a local phone number." Oftentimes, the operator will send you an SMS with a one-time password, but they require a local phone number to send it to. Or they use your phone number to de-anonymize you, so it must be a phone number from their local country. When traveling, this makes these "open" access points effectively useless, unless you decide to spoof another person's MAC address.