A recent change in Spring Framework 7.0 snapshots deprecated messageConverters(List).
I believe the intention of this customizer is to only add the configured converters and, if they aren't any, then let the standard behavior of registering default converters from framework.
As noted by the deprecation note, we should use configureMessageConverters(Builder) instead. However, using this method seems to register the default irrespective of us providing some converters.
I've suppressed the warning for now in https://github.com/spring-projects/spring-boot/commit/0efe9c271b5fbe2bf7f95d174816c72650027fa8 as we need to figure out if a change in framework and/or boot is required.