Here is a way to override the configuration of the auto-configured ObjectMapper object.

package com.vianneyfaivre.config;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;

import java.util.TimeZone;

* Overrides the default Spring Boot configuration of Jackson JSON {@link ObjectMapper}
public class JsonConfig extends MappingJackson2HttpMessageConverter {

    public JsonConfig(ObjectMapper objectMapper) {

        // TODO: here you can do whatever you want with the objectMapper object 

        // Example of configuration: Set default timezone when serializing/deserializing dates

Tested with Spring Boot 2.3.