Same here!

This works in Monterey final release. brew install macchanger And then (with your network disconnected): macchanger -m xx:xx:xx:xx:xx:xx en0 Replacing the xx with your required MAC address and en0 with the appropriate network device.

The Screen Time hack no longer works it seems. The problem now appears for me every time I plug in an LG 5K monitor and to resolve it you must reboot with the monitor still plugged in. Confirming also this issue still exists in 11.0.1, which I assume therefore means it will be in 11 GM. Apple better be ready for an awful lot of unhappy 5K monitor owners.

Disable Screen Time and reboot to solve this issue.