In new operating systems iOS 18, iPadOS 18 and macOS 15 Sequoia the company has replaced the Private Wi-Fi Address option with a new feature called Rotate Wi-Fi Address. It is designed to minimize the possibility of tracking.
Apple says that the Rotate Wi-Fi Address feature is available when you access the settings of any Wi-Fi network. It changes your Wi-Fi address at random times.
Changing your Wi-Fi address helps reduce the likelihood of tracking. Tracking can occur when your address always appears the same to other devices and people who use the same network as you.
The previous Private Wi-Fi Address setting assigned a different MAC address to your device for each Wi-Fi network it connected to.
Rotate Wi-Fi Address, like Private Wi-Fi Address, is a separate feature from the additional option Limit IP Address Tracking, which you can enable for Mail and Safari.
Source: macrumors