If you're not using Certificates for user authentication, it will not be considered as 2 factor.
You just need to generate CSR, get your ID and CA Certficates and import them on ASA. It will help clients validate the ASA url and will not give you "untrusted" message when you try to connect.
Under tunnel group, add radius server as authentication server group and you should be good to go.
Regards,
Puneesh
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