Really easy to spoof the serial number. Most copiers wouldn't be running on a 3A+, so that would help a bit.
I know it's not going to be bullet proof. But, I want to do what's easy for me to do.
RPI3A+ does not have ethernet.pi@HeatTracker:~/HeatTracker $ cat /sys/class/net/eth0/address
cat: /sys/class/net/eth0/address: No such file or directory