Implement a new solution: Instead of static code blocks disabling logging, rollback slf4j-api, logback-classic, and logback-core to older versions. It's the addition of the rollback for slf4j-api that seems to restore logging.

src/test/java/ca/uhn/fhir/jpa/starter/ElasticsearchLastNR4IT.java

@@ -57,10 +57,6 @@ import org.testcontainers.elasticsearch.ElasticsearchContainer;
   })
 @ContextConfiguration(initializers = ElasticsearchLastNR4IT.Initializer.class)
 public class ElasticsearchLastNR4IT {
-	static {
-		System.setProperty("org.springframework.boot.logging.LoggingSystem", "none");
-	}
-
 
 	private IGenericClient ourClient;
   private FhirContext ourCtx;