As far as I can see, the only way WiFi Guard can detect unknown clients on a WiFi network is by MAC address. Recent updates from Apple (iOS 14 and iPadOS 14) have defaulted many of their products to use "private MAC addresses" which frequently change. This results in frequent false alerts about new users on the network whenever an iPad or iPhone connects. Is there a solution, or does this break the monitoring of WiFi Guard?
Normally, only the last three octets of a MAC address change in those "private Wi-Fi addresses", while the first three octets stay the same.
To deal with this, you can use the Partial match feature on the Advanced tab in WiFi Guard settings, as shown below. It basically lets you automatically approve any MAC address that starts with XX-XX-XX, the stable (unchanging) part of the MAC address of your device. Then even if the last three octets change, there would be no false alarm.