[SOLVED]

I've resolved creating a Bean of type ObjectMapper instead of passing it to the JsonSerializer constructor during the DefaultKafkaProducerFactory Bean definition.

@Configuration
public class ObjectMapperConfig {
    @Bean
    @Primary
    public ObjectMapper objectMapper() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
        return mapper;
    }
}