Since I cannot provide direct file links (they expire frequently and depend on your specific board), here are the best repositories to search:
The CoreELEC website provides generic images for Amlogic devices. For S905L2, you would typically download the "Generic" image ( CoreELEC-Amlogic-ng.arm-xxx-Generic.img.gz ). The official wiki explains that you burn this image to an SD card, then browse to the "Device Trees" folder to select the appropriate .dtb file for your specific device. amlogic s905l2 firmware link