If you need to register extended scalars with the new Spring Boot GraphQL Starter (see) just provide a custom "RuntimeWiringConfigurer":

Kotlin example:

@Configuration
class GraphQLConfigProvider {
    @Bean
    fun configureGraphQL(): RuntimeWiringConfigurer {
        return object : RuntimeWiringConfigurer {
            override fun configure(builder: RuntimeWiring.Builder) {
                builder.scalar(ExtendedScalars.Date)
                // ...
            }
        }
    }
}

Register the scalar in your schema:

scalar Date

type XYZ {
date_entry : Date
}

Notes:

You need to include the extended Scalars in your POM/Gradle file (mvnrepository):

implementation("com.graphql-java:graphql-java-extended-scalars:17.0")

Happy querying ...