Those without phones can use a security key for DUO. December 06, 2021 15:40 Updated Must have a U2F security key to complete the process. A supported USB security key. WebAuthn/FIDO2 security keys from Yubico or Feitian are good options. Go to https://guide.duo.com/security-keys for online instructions to enroll in Duo 2-factor authentication with a security key. Related articles How to add new phone to DUO mobile with the same phone number. I don't have a phone or access to a phone for DUO. Hardware tokens are available. How does a guest connect to campus WIFI.