Hi.
SMB requires Kerberos or NTLM authentication which I believe OKTA do not support.
Likely can do with the built-it option that mentioned here
https://support.okta.com/help/s/question/0D51Y0000A2St5KSQS/smbfileserver-access-through-okta?language=en_US
Another option is to maybe login into some terminal server using the OKTA, and allow access to the files on ONTAP only from that terminal server.
https://help.okta.com/en/prod/Content/Topics/Security/proc-mfa-win-creds-rdp.htm