If your MacBook is locked at the BIOS/Firmware level (a black screen with a padlock), the "free" update is a bit simpler:
Bypassing security measures often disables features like Apple Pay, Touch ID, and official macOS updates. The Ethical Bottom Line macbook t2 bypass free upd
: Permanent or untethered licenses for T2 Macs generally start around OS Support If your MacBook is locked at the BIOS/Firmware