[grizzledyoungman]

All -

I think I got the HDMI CEC suspend/ARC issues sorted out and wanted to share my solution here, both to confirm that it's a good solve and to make it available for others.

Part 1.  Disable HDMI CEC on CoreELEC.

1. Disabled HDMI CEC completed in System-Input-Peripherals-CEC Adapater
   
2. Disabled all CEC settings in Corelec-Hardware-CEC.  All remain disabled after backing out of the menu except for "CEC Wake-up" which reverts to odd.  Not sure what that's about.
   
3. Using the method provided here for editing the config.ini file, I removed the comment for HDMI CEC and set it to "0" 
   
4. Now the various HDMI/ARC issues went away   ARC is reliably available and HDMI routing issues are gone.
   

Part 2: Use Harmony Hub to make the Odroid suspend when not in use.

1. I added the Odroid N2 as a device in my Harmony Hub setup.
   
2. I added the Odroid N2 to the Harmony remote activity for CoreELEC.
   
3. I configured the Harmony remote activity to send the Odroid N2 an on/off signal during activity start/stop.
   
4. Back in the CE menus, I configred System-Power Saving I changed "shutdown function" to "suspend."  Now IR power toggle puts the Odroid N2 into suspend instead of off - much faster
   
5. I also configured a button on my Harmony remote to fire the IR power toggle command, just in case I need to manually power it on.
   

Thoughts on this fix?  Have I done anything that would contradict best practice?  Is using the IR power toggle this way harmful to the device?  I vaguely remember reading that the IR power toggle in CE doesn't always trigger an orderly shutdown or suspend.