Most mid-range OPPO phones (A series, A53, A54, etc.) use MediaTek processors. These chips have a secret "BootROM" mode that can be accessed by holding specific volume buttons while connecting USB. The Flash Tool sends a hacked "DA file" (Download Agent) to the RAM, which allows reading/writing to the NAND flash memory. This bypasses the lock screen security entirely.
: Switch from ColorOS to cleaner, "stock" Android experiences like LineageOS. Gain Root Access oppo flash unlock tool