How to import Office 365 guest accounts into OKTA universal directory
The OKTA provided "Office 365 Application" will not import existing Office 365 Guest accounts. It will only import licensed Office 365 accounts. Thus there's not a way for Office guest accounts to authenticate through OKTA.
As far as we can confirm guest accounts are accounts from outside of your company. In order for us to import any user that account needs to have a valid email address, first and last name. You can attempt to create an account for them in Okta but as the email address will be out of Office domain we will not attempt to link the account( as account is not Office user) and we will attempt to create a new user based on the information. You can expect that to fail.