Specialized tools exist that plug into the HDMI port or USB port to trigger download mode without opening the case. Search for "Amlogic no-disassembly shorting tool" if you prefer to avoid soldering.
Before you search for “Amlogic S905L2 firmware fixed,” you must know your PCB (Printed Circuit Board) revision. Flashing the wrong fixed firmware can permanently brick your device because the GPIO pins for Ethernet, LEDs, and IR receivers differ. amlogic s905l2 firmware fixed
Next to the S905L2 CPU, find a small square chip. Common IDs: Specialized tools exist that plug into the HDMI