Swan 
More than half of the SEO effectiveness of a SEO service comes from the power of the links you receive from other websites. If, at the time of a site migration, with or without domain name change, you do not pay attention to the redirection of these links, you expose yourself to a dramatic loss of notoriety with Google.
Data recovery
To avoid losing this notoriety, we advise you to recover as much data as possible either in the console or in a backlink tracking tool offered by Semrush, Majestic or Ahrefs.
Also, by setting up 301 redirection, you are telling Google that the old URL now refers to a new address. It will then be able to forward the notoriety of the old site to this new address and you will considerably reduce the risk of losing traffic during the migration of your website.
Sources of information
It is important, on the one hand, to multiply the sources of information. On the other hand, you should not only take the home page, which is likely to remain static. The reason is that you might lose links to pages that were previously orphaned or even non-existent since a previous operation. Performing a complete analysis during this migration may even be an opportunity for you to rediscover backlinks you didn’t know before. Moreover, you may not have used all the backlinks and some may have arrived naturally. Also, it is important to get help from different tools to make sure you don’t lose any links.