Different manufacturers use different protocols. Below are the specific workflows for the most popular brands, none of which require a SIM card.
Unlocking the bootloader is the first step toward rooting, installing custom ROMs, or gaining full system-level access on Android devices. Normally, many manufacturers (like Xiaomi, Samsung, and OnePlus) require a SIM card to be inserted—often for account binding, OEM unlocking validation, or carrier verification. how to unlock bootloader without sim card
Open a Command Prompt or Terminal window inside your Android SDK Platform Tools folder. Different manufacturers use different protocols