The recently added setTaskScheduler returns void instead of StompBrokerRelayRegistration and so does setTcpClient which was added longer ago might be worth addressing.
Originally reported in https://github.com/spring-projects/spring-framework/issues/22822#issuecomment-723735475.
Comment From: jhoeller
Let's address both in 5.3.1 indeed. This is still early enough, in particular since the change is source compatible (just not binary compatible), so fresh application builds won't see any regression.