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/main/java/ca/uhn/fhir/jpa/starter/Application.java

@@ -38,10 +38,6 @@ import org.springframework.web.servlet.DispatcherServlet;
 })
 public class Application extends SpringBootServletInitializer {
 
-	static {
-		System.setProperty("org.springframework.boot.logging.LoggingSystem", "none");
-	}
-
   public static void main(String[] args) {
 
     SpringApplication.run(Application.class, args);