Followed Erbas's instructions, but new problem erupted. When I insert the microSD card, and depress the "reset" button, my box boots into TWRP. Same thing if I type "reboot update" from a terminal emulator.
I am using Alvatech's ATV ROM, which has a builtin TWRP. Just did a clean install yesterday.
I'm using beelinks official firmware, if it doesn't boot to a sd/usb image just use "switch os" reboot option under android then it works for all third party firmwares.