goa

For 1: The red led can be turn off or used for any other purpose. I am not at home so I cannot tell you the exact location but simply do something like du -a /sys|grep led and search for the orangepi red led and trigger. For example you can do echo heartbeat > trigger and it should flicker.
For 2: Odd. As for me I never used the HDMI on it as I prefer SSH as well. Though you can give either an older or a newer dev build image a shot and check if anything changes. Makes it easier to track it down. You may also want to provide an armbianmonitor -u output here.
For 3: No idea.

Thanks for providing the new Buster image (5.4.7) for Orange Pi One Plus. All the essential stuff works well, giving me new software possibilities.
 
As a technical feedback, I'd just like to mention
1) the red light keeps shining (instead of turning green, but Armbian runs very well, anyway)
2) an attached monitor doesn't receive any signals (but I prefer SSH anyway)
3) the console keyboard layout wouldn't accept any changes (but using SSH, that doesn't make any difference now).
 
Everything else in armbian-config worked fine. Great tool!