akira... Done further testing...TLDR, get a different airmouse.

*The Power, Menu & Task Manager buttons don't function either.
*Back button doesn't work unless in airmouse mode. This being a frequently used button.. I eventually had to ditch the Minix Neo A2 Lite Airmouse in favor of the included remote and a Logitech Keyboard + Mouse combo.
*Media related buttons and keyboard on the other side all work.

Newsletter

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The GT King series now supports a dual system plan. Both the Regular and the Pro versions now support dual-booting Android & CoreELEC. CoreELEC for the uninitiated is a ‘Just enough OS’ Linux distribution based on Kodi technology for popular AMLogic hardware. There's a stable (Latest version being CoreELEC 9.2.0) and nightly versions. Beelink in the past reached out the the CoreELEC dev team and have been working in-depth behind the scenes for compatibility. The time is here and the GT-King series are officially supported by the CoreELEC dev team. Promises have been made to have more Beelink products adapted to this dual-booting system. I'll update as time goes on, which devices become supported.

CoreELEC Pre-Installed
In order to thank users for their support for our products..An 8GB SD/TF card with CoreELEC system pre-installed will ship with future sold units of the GT-King series... So one only has to insert the SD/TF card in our GT-King series products. The CoreELEC system can be used immediately with minimal fuss. Take note, I'm unsure how long this free and pre-installed SD/TF card deal will continue. So interested parties should grab it while they can.

Switch freely between OSes
Being a dual-booting system, it's important to note that switching between both OSes is made even simpler. This is to aid users to switch freely between the Android AOSP system and the CoreELEC system. Just press and hold the power off button of the remote control, and the System switch option will appear as shown in the figure below. Select this option and confirm, the machine will restart into the CoreELEC system located in the SD/TF card.

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As time goes one, we will endeavor to adapt this feature to more devices. If there's a model you'd like to see such on, you can also contact us. We will try to contact the corresponding developers to adapt it for the products.

How to use the dual OS system.
Booting into CoreELEC
Create yours or insert the supplied SD/TF card into the card slot, connect the power and turn on the machine. The CoreELEC system will boot up automatically. From this, we can deduce that as long as the SD/TF card is inserted, the first/default boot option is CoreELEC.

Stock Android to CoreELEC
So you are already booted into Android and would like to switch to CoreELEC. Just insert the pre-loaded card.. Press and hold the power off button on the remote control.. Select the "System switch option", and allow the system to restart into CoreELEC OS.
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CoreELEC to Android
In this instance, one already booted the CoreELEC OS and would like to switch over to the Android OS. Simply select the "Reboot from to eMMC/NAND" option from the Power menu. The system will reboot into Android automatically.
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Alternatively, launch the main menu, enter the exit option, select the "Reboot from NAND" option. This should initiate a restart and boot into the Android AOSP system.

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Updating the CoreELEC OS
Firstly download the incremental package file. Then copy this downloaded file to the /storage/.update folder on the device. Restarting the device will initiate the update. Bare in mind that on the STABLE version can be automatically updated in the system. The nightly version involves manually updating the core files.

CoreELEC official website
For more information, please pay attention to Beelink's official website