I can get into M-Horse S51 using Linux and adb thru the adb reboot recovery command
I have tried various combinations of volume up or down with power buttong with or without the "camera" or middle button
Power button for a couple of seconds until first animation.....release then hold down volume down gets me to safe mode.
Does anyone know how to get into recovery mode by buttons?
here is proof of adb working......as you see its a combined factory mode/recovery mode