Where to find "Firmware password" option to turn it off before selling MacBook?

see if this article adds insight:

This feature requires a Mac with an Intel processor. For the equivalent level of security on a Mac with Apple silicon, simply turn on FileVault. If the Mac is managed by MDM (mobile device management), the MDM administrator can also remotely lock the Mac.

from:

Set a firmware password on your Mac - Apple Support

Alejandro_64 wrote:

You sure there's no more Firmware Password anymore?

I could swear I've locked the device with it right after the purchase...

Will it be sufficient to take the steps described in this article for the buyer not to have any probs with pw? What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

checks to see if the firmware password is set(?)

check for Firmware password set..from the Terminal.app copy & paste:

sudo firmwarepasswd -check

you can verify you have the correct password (without rebooting).

sudo firmwarepasswd -verify

deletes the firmware password. You'll need the current one to delete it, of course.

sudo firmwarepasswd -delete

Alejandro_64 wrote:

"Firmware password" - no such option in "Utilities" menu anymore in Recovery mode. Just no such option at all!

MacBook M1 Pro 13. Sequoia 15.7.2.

Preparing the device for selling - and can't figure out how to turn Firmware Password off.

Any clue?

I’m guessing that you saw a FileVault recovery password, and not a firmware password.

Related: FileVault recovery options - Apple Support

Mac with Apple silicon (such as yours) can have a Recovery Lock (RecoveryOS lock), though that’s almost always a managed or supervised Mac.

Startup security in macOS - Apple Support

You can test for a RecoveryOS password by booting Recovery:

How to start up from macOS Recovery - Apple Support

If that RecoveryOS password is set, and is forgotten, then you’ll likely need to prove ownership to Apple to get that removed. That usually means providing an original purchase receipt, and a discussion with Apple Support.

Alejandro_64 wrote:

Will it be sufficient to take the steps described in this article for the buyer not to have any probs with pw? What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

Yes.