If you cannot toggle "OEM Unlocking" in developer settings:
Samsung devices sold in the US and Canada (Snapdragon variants) are historically locked tight. Unless you find a paid 3rd-party exploit, these usually cannot be unlocked. Step 2: Enable Developer Options and OEM Unlocking
On newer Samsung devices, simply unlocking isn't enough. You may encounter a "Vault" or "Prenormal" status that prevents you from flashing custom files immediately. Set up your phone as new (skip the Google login for now). Connect to Wi-Fi.