Error configuring SAML Tableau Server with Keycloak as IdP

Does anyone have any experience with configurating Keycloak as an IdP for Tableau Server with SAML ?

Here is an error message that I have in the Tableau Server logs after trying to connect :

2021-05-25 12:17:52.312 +0200 (-,-,-,YKzOz8q-Qn9yFf5gruC2EAAAAfk,f97281fd-927e-4759-a1c5-6668da4832aa) catalina-exec-16 auth_saml: ERROR com.tableausoftware.samlauthentication.handlers.SAMLAuthenticationFailureHandler - SAML Authentication Failed, please contact the administrator. Incoming SAML message has no valid value for username attribute. Please verify ServiceProvider configuration in Identity Provider.