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.