Switching my Argon One M.2 off and on with my Logitech Harmony 650 works with following procedure:
- Get an Argon IR Remote (you will need this to learn the Harmony the ON comand when th Raspberry 4 with LibreElec is offline)
- Use Harmony Software to learn the new PowerOn command (navigate to Mecool KIII pro -> Add or modify command -> click on "Add missing command" -> Type PowerOn -> Accept -> Follow the provided procedure to learn the new command
- SSH into your Raspi
- In file mecool change the Line containing 0x59 KEY_POWER into 0x59 KEY_POWEROFF using nano or whatever editor you prefer.(this is necessary because we must change the PowerToogle behaviuor to use seperate Keys for PowerOn and PowerOff)
- Back in Harmony Software, if you have not done this yet, create an Action or your LibreElec setup (I just named it LibreElec) with Your TV set, Surround Receiver (if you have one)
- In your Action (LibreElec) change the startup order with the mecool device to start and shutdown first, otherwise you may run into problems
- If you have startup/shutdown problems. go into Harmony software -> device -> modify device settings -> Usage settings? (in German this is called Betriebseinstellungen) -> on the next page do NOT use the options "There is no on/off switch on the Remote of my mecool-dvr" (your argon device) or "I want my device to be switched on everytime". The other two options are a kind of personal taste
- Now you should be asked wether your Original Remote has One Key for Toggle On/Off or two seperate Keys for switching your device On and Off. Just Lie and click the "I use two seperate keys to switch my device On/Off" button
. - On the next page you have only to assign your PowerOn comand to the On commands and your PowerToggle command (what is thanks to the modifikation in step 4 now ou PowerOff command) to the Off commands. I used 0,5 s for the timing to give the commands a proper chance to execute
- When all (hopefully) is working well, enjoy
I sadfully had to translate the Pages of the Harmony Software from German to English, so don't beat me if the options in this Software don't match the english version 
