There is a new (?) Android image for the A5X Max+ https://www.chinagadgetsreviews.com/download-android-nougat-7-1-1-firmware-a5x-max-tv-box.html
It does not seem to be a disk image but rather some kind proprietary upload format:-(
I'm currently trying to dump the emmc to an USB stick. Let's see, if that shows something?!