I don’t think this is down to macOS version, it seems related to the vintage of the hardware. I have a Late 2016 15” which allows me to change the MAC address,

I don’t think this is down to macOS version, it seems related to the vintage of the hardware. I have a Late 2016 15” which allows me to change the MAC address, and anything 2018+ does not seem to allow it. Both the 2018 and 2019 model return zero when you type “ifconfig” commands to change the hardware address, but the command has no effect. Have tried this on Mojave and Catalina.