For users who would prefer not to use a mobile device to authenticate their login attempts, it is possible to use a physical key instead. A key is a small device that verifies your identify when you press a button. In order to use a key it must be WebAuthn or U2F compliant.
You can purchase keys online from a variety of vendors such as:
https://www.yubico.com/gb/store/
https://cloud.google.com/security/products/titan-security-key
[note these links are provided purely for convenience and we do not recommend or endorse any particular supplier or brand].
Please see this Salesforce Article for instructions on how to register a physical key:
https://help.salesforce.com/s/articleView?id=sf.security_u2f_register_security_key.htm&type=5