Right now, if people register for an event, it has to be "paid" or "free." There is no way to offer a hidden free ticket to a paid event. A hidden ticket and promo code mitigates that issues and allows participants to seamlessly register.

A possible workaround is a second free event that is hidden and not publicly advertised. However, then you have two events to track instead of one, plus users still cannot copy/replicate Events in RENXT.