There's a "use different authenticator app" button, but it can be disabled by the domain admin and that might be the default depending on when your Azure AD dom

There's a "use different authenticator app" button, but it can be disabled by the domain admin and that might be the default depending on when your Azure AD domain was set up. The fact that you can set a domain to MSA/TOTP or MSA-only, but not TOTP-only, is an incredibly scummy, but incredibly predictable move by MS.