The Star Alliance Reference Guide is abundantly clear that a BP showing *G is sufficient for lounge access. An airline gold card is only required should the BP not show *G...
Reference Guide - Airports Information - Lounge Access
"Star Alliance Gold (SAG) customers travelling in any class on Star Alliance flights
Star Alliance Gold customers have access to any member carriers' owned lounge that displays the Star Alliance Gold logo. Customers will need to present a boarding pass for a Star Alliance flight departing from the local airport. If the boarding pass does not carry the Star Alliance Gold indicator XX*G, the customer will need to also show a valid Star Alliance Gold card. Customers are entitled to a maximum of one guest. Restrictions apply for United MileagePlus Star Alliance Gold customers wishing to access United Clubs within the U.S., who may only access the United Clubs within the U.S. when travelling in conjunction with an international Star Alliance flight. In cases of discrepancy between the loyalty status level displayed on any form of identification presented for lounge access by the customer and what is displayed in the Star Alliance Premium Customer Database, the highest displayed level will be honoured for lounge access and billing purposes. If no XX*G indicator is displayed on the boarding pass and a manual PCD validation of the Frequent Flyer Number is performed by the lounge staff, the status displayed in the PCD will be honoured for access and billing purposes. In the event no manual PCD validation can be performed, the status displayed on the FFP card will be honoured."

You may wish to carry a PDF copy of the guide to stop lounges trying to ignore the official rules ...

https://portal.staralliance.com/empl...eference-guide