If you attempt to set up a separate Named Instance in SQL Server and assign it a different TCP Port and attempt installation, you may run into an error message such as the following:
If you try to install with the Default port entered ('1433'), with correct credentials, Yellowfin will let you connect and attempt installation, but the installation itself will fail.
Based on the Microsoft documentation for Configure a Server to Listen on a Specific TCP Port, one of the required steps is that "when you are connecting to a named instance through a firewall, configure the Database Engine to listen on a specific port, so that the appropriate port can be opened in the firewall."
As such, the new port has to be opened in the Firewall before this can work as intended. Steps to accomplish this can be found in the Microsoft article linked above.
If you have any additional questions please either reach out to Yellowfin Support for further assistance, or reference additional Microsoft documentation.
As a reminder/additional pointer, if you can't connect to the instance via a third-party db tool such as DbVisualizer, the connection won't work in Yellowfin either and must be addressed from the db-side: