If the firmware lock was triggered by "Mark as Lost" in the Find My app, you can often remove it by logging into iCloud.com , selecting your device, and entering the 6-digit PIN you created when locking it.

For those who are interested, the command used to remove the EFI password was:

Note: This does work on any Mac where the RAM is soldered to the motherboard (which includes almost all modern MacBooks). 4. For T2 and Apple Silicon (M1/M2/M3) Macs

(or add one if you have a spare).