Providing that you have the original Android 6 firmware for your box to fall back on, you should be able to attempt installing generic S905X android 7.x firmware to your device. Something like Aidan’s Rom or the firmware quoted in the linked thread would be a decent place to start. The topic has been covered pretty throughly in various threads on this forum.
Here’s a place to start:
https://discourse.coreelec.org/t/testers-wanted-gxl-1gb-ram-devices-amlogic-ng/15877/3