Whilst MAC address Randomisation has been with us since Android 10, it was turned on by default when joining networks with iOS 14. This has had an impact on companies that use MAC address auth, or features like Meraki Sentry (which uses Systems Manager).
So, firstly, you can use Systems Manager to manage this with iOS:
https://youtu.be/Bj9Gg7h50Gk
But I also wanted to put some background with regards to the OS support for MAC randomisation:
Windows:
Can be turned ON for Windows. It’s either included, or not included, depending on the version of windows, and depends on the WiFi network card vendor
It can be done by network, or system wide
https://support.microsoft.com/en-us/help/4027925/windows-how-and-why-to-use-random-hardware-addresse...
https://support.microsoft.com/en-us/help/4578384/why-use-random-hardware-addresses
Android:
From Android 8.0, Android devices use randomised MAC addresses when probing for new networks while not currently associated with a network. In Android 9, you can enable a developer option (it's disabled by default) to cause the device to use a randomized MAC address when connecting to a Wi-Fi network.
In Android 10, MAC randomization is enabled by default for client mode, SoftAp, and Wi-Fi Direct.
https://source.android.com/devices/tech/connect/wifi-mac-randomization
iOS / WatchOS / iPadOS
Apple added MAC address randomization to its devices starting from iOS 8. In iOS 8, randomized addresses are only used while unassociated and in sleep mode. iOS 9 was extended to also use randomization in what Apple calls location and auto-join scans.
Use private Wi-Fi addresses in iOS 14, iPadOS 14, and watchOS 7: https://support.apple.com/en-gb/HT211227
macOS:
macOS does not appear, at this time, to use randomisation for MAC addresses
Background:
http://papers.mathyvanhoef.com/asiaccs2016.pdf
