How to get a list of WordPress default database tables?

There is no programmatic way to get a list of default tables. WordPress does not store a list of them anywhere. The closest thing there is is wp_get_db_schema(). This function returns the raw SQL used to create the default tables, but as you can see from the source, it doesn’t derive it from another source, it is where the default tables are originally defined. Maybe you could parse the SQL to figure it out, but I’m not sure why you’d need to.