First of all I would like to say hello.
To the point. I have Mecool M8S PRO W with Amlogic S905W. I installed Android TV Nexus 7.1 from this site: [ROM] Mecool M8S PRO W TVStock Nexus ROM (Android TV 7.1) - FreakTab.com
With it there is installed TWRP Recovery. I would like to test LibreElec (boot from SD Card, not installing) and I have little problem. The only way I can reboot to recovery is "terminal emulator" method by using "reboot update" command. I don't have reset or menu button, don't have "update" app. So I used terminal emulator to reboot recovery but after this it runs TWRP. What should I do to boot from SD Card in this case?