Spring Boot 2.4 is based on Spring 5.3 and runs with Java 15.
In Spring Boot 2.3, we could create Docker images out of the box. With Spring Boot 2.4, we can push these images to a Docker repository, like Docker Hub. See the Maven and Gradle plugin documentation for details.
The config file processing was overhauled. Simple config files should stay the same. But we can now import configuration trees that are often used with Kubernetes. See this migration guide for details.