Erasing Macs

Create Bootable Install Media

sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled

Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing. A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.
Turn on the Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes.
Select the volume containing the bootable installer, then click Continue.
When the macOS installer opens, follow the onscreen installation instructions.

Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing. A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.
Turn on your Mac, then immediately press and hold the Option (Alt) key.
Release the Option key when you see a dark screen showing your bootable volumes.
Select the volume containing the bootable installer. Then click the onscreen arrow or press Return.
If you can't start up from the bootable installer, make sure that Startup Security Utility is set to allow booting from external or removable media.
Choose your language, if prompted.
Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Select Erase Mac… from the Recovery Assistant menu.

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Return to Service - Leave the Mac assigned to MDM.

Disposal - Unassign the Mac before reinstalling macOS so that it does not download the activation record pointing to enroll into MDM.

Double click “Install macOS ….” and follow on screen instructions for the installer.

Shutdown after getting to the Welcome screen.