Okta as Azure APIM Developer Portal Identity Provider

The organization is already using Okta as its IdP.
Now we have a requirement to secure Azure APIM Developer Portal by using Okta. We want to avoid solution where Azure AD B2C is using Okta as its federated IdP which is feasible. MS suggests using Delegate authentication approach, but there are no details on Okta side how to achieve that.

Any idea?