How can I migrate SMS/MMS history from the stock Galaxy s6 app to Google Messenger?

[AC Question]

I transferred my SMS/MMS history from my ancient Moto X (first gen) to my new Galaxy s6, but the history is only accessible from the stock Samsung messenger, not the Google Messenger app. I'd like to see my whole text history in Google Messenger. Any help to figure out how to import the history into Google Messenger would be greatly appreciated! Thanks.