I want to set up multi-factor authentication for CAS outside of my phone's authentication app.
CAS multi-factor authentication requires the setting of an authentication application.
In addition to a smartphone, an authentication application can be set up on a PC.
CAS multi-factor authentication does not have the ability to send one-time passwords (six-digit numbers) to phone numbers, SMS (short message service), or email addresses.
If you do not want to use an authentication application at all costs, use a hardware token.
https://icts.nagoya-u.ac.jp/en/services/nuid/CAS/mfa_cas_HWtoken_registration.html