On a rooted/jailbroken phone, there are apps that just dump the database into a readable format.

Theoretically you might be able to get something out of the local or cloud backups, but they're encrypted so they're probably difficult to get a hold of. The key is stored in the private application data, but there must be some way to get it back/regenerate it because you can restore a backup without copying any secrets from the previous phone.

Actually I bought a piece of software [1] that perfectly exported five years of messages out of my cellphone, then I didn’t hesitate once day to delete my WhatsApp accout.

[1]: „Backuptrans iPhone WhatsApp Transfer for Mac“