Thank you for posting this in Microsoft Q&A.
I understand that you want to integrate WordPress with Entra External ID using SAML SSO.
Currently, the external tenant supports only the OpenID Connect and OAuth2 protocols, it does not support the SAML protocol.
For more information regarding supported features in external tenant: https://learn.microsoft.com/en-us/entra/external-id/customers/concept-supported-features-customers#compare-workforce-and-customer-tenant-capabilities
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Navya.
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