MFA with TOTP without FortiToken?

You can 2FA with email or with RADIUS server:

With email:

config user local
   edit "user"
       set type password
       set two-factor email
       set email-to "user@domain.com"
   next
end

With RADIUS: We are OpenText clients with NOWS subscription (older Novell). This bundle includes NetIQ Advanced Authentication that lets several source directory and serves RADIUS with MFA (TOTP, SMS, email, etc)