Here is my solution for making Amlogic S812 based Beelink MXIII Plus Android TV Box work with Logitech Harmony universal remote. It’s based on solution described on this forum post, but modified to make it easier to use (if your Harmony remote is able to learn new IR commands).

Step by Step guide

NOTE: ssh/terminal access with root on the TV box is required

1. Download new remote config from here to your Amlogic TV box. Store it in the /sdcard directory.
2. Download start script from here to your TV box. Store it in the /sdcard directory.
3. Follow modification described in remote config, but don’t replace existing remote.conf file.
4. Install Script Manager app from Play Store.
5. Set Script Manager to launch on android boot, and to have root privileges.
6. In Script Manager locate our sh script, and configure it to be started on boot and to run under root.
7. In MyHarmony add new device  ‘Pivos XIOS DS Media Player‘
8. Go to this device, choose Add or Fix command and select to Fix PowerToggle command
9. Follow the wizard, and let harmony learn Power button on original Beelink remote
10. Modify device delays – set all values to 0 to speed up remote
11. Change power buttons functionality off the device, configure it like it would have two different buttons for power-on and power-off. Modify power-off sequence to send also ‘OK’ after PowerToggle command (this is necessary because TV Box shows shutdown dialog with Hibernate/Shutdown options instead of simple powering down).
12. Now you can configure your activity…

All the magic lies in ‘factory_infcode = 2‘ directive in our remote config. This registers 3rd remote to system, without replacing the original one(s), and therefore we can use commands from that remote(s) on Harmony to power it on/off. As a bonus, original remote(s) will still work and you can use them when needed.