Try the latest image: https://relkai.coreelec.org/CoreELEC-Amlogic-ng.arm-9.1-nightly_20190722-Generic.img.gz
Make sure you use the -ng version and use an S905X2 dtb from device_trees folder.
Copy it to the root of the card/pendrive and rename it to dtb.img.
Visit this topic for further info: Support added for S905X2, S922X and A311D!