The easiest way to connect wordpress to a second database (without a token) is to add this little piece of code (replacing strings by your connexion data) :
$wpdb2 = new WPDB( 'remote_user', 'remote_password', 'remote_db', 'remote_server');
Then you can use this new object to query anything that you want to, just like the main $wpdb object. You can use this on the function.php file of your active child theme (or theme).
I think that maybe there is some plugins, for this kind of purpose… You will have to search.
Reference: Using wpdb to connect to a separate database
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