I bought a cheap (and crappy) box from ebay. It says "M9S Pro 16G" on it; the reset button is behind the spdif socket (not the av socket). It was sold as having 2 gb ram, but there is only 1 gb.
There was no dtb partition, but a trawl through /dev/mmcblk0 under android I found the attached six dtbs. Of these, the one I've named gxl_p242_1g corresponds to the contents of /proc/device-tree.
Libreelec seems to run OK with a p212 dtb but I wonder what is different in the other dtbs here. I can't find any reference to p242 with google.