(…unless you run with "sudo")
Luckily, you can still get the MAC addresses with
networksetup -getmacaddress en0 % /bin/bash --version
GNU bash, version 3.2.57(1)-release (arm64-apple-darwin26)
% /opt/homebrew/bin/bash --version
GNU bash, version 5.3.20(1)-release (aarch64-apple-darwin27.0.0)
% zsh -c '/sbin/ifconfig en0 | grep ether'
ether d0:11:e5:1a:27:7a
% /bin/bash -c '/sbin/ifconfig en0 | grep ether'
ether d0:11:e5:1a:27:7a
% /opt/homebrew/bin/bash -c '/sbin/ifconfig en0 | grep ether'
ether 02:00:00:00:00:00