Open Keycloak

Select Clients / Select the SAML Client and Select Mappers

Add the X500. givenName, sureName and email

Open the Application

Configure the Authentication

For the username you can use

urn:oid:2.5.4.42 + " " + urn:oid:2.5.4.4

This will concatenate the X500 givenName and the surame

For the email you can use the X500 email

urn:oid:1.2.840.113549.1.9.1

You can also define the default usersgroups that a new user will be added to