Unlike many other Android devices (e.g., Google Pixel, OnePlus), Samsung phones do not use a standard “Fastboot mode.” Instead, Samsung devices use Download Mode (also known as Odin Mode) for low-level firmware flashing, unlocking, and system repairs.
Here’s a clear, step-by-step write-up on how to access on a Samsung Galaxy A12 . How to Open Fastboot Mode on SAMSUNG Galaxy A12
If your goal was simply to unlock the bootloader or install custom recovery (TWRP), Download Mode is the correct first step. Unlike many other Android devices (e