apply_filters( 'relevanssi_attachment_server_url', string $server )
Allows changing the attachment reading server URL.
Parameters
$server
(string) The server URL, defaults to Relevanssi US or EU server URL, depending on your settings.
More information
If you’re looking to replace the Relevanssi attachment reading server with your own, you need to use this filter hook to let Relevanssi know where your server is located.
add_filter( 'relevanssi_attachment_server_url', function() { return 'https://localserver:8000/'; } );
Use the directory name as the value; Relevanssi will add index.php
to the URL later.