I use Librelec on my Odroid-C2 to play 4k content. It supports DCI 4k at 60fps and it is slightly more expensive than a RPi4.
The blue LED functions as a sort of hearbeat. It is somehow linked to kernel activity in way that I’m not entirely sure. If it blinks like crazy all is well. However, the blue LED is quite bright and quite annoying to dark adapted eyes. It doesn’t help that I don’t have a case for my newest Odroid-C2 (last one abandoned with the rest of my old life in Thailand).
The way this was addressed by odroid is one of the many reasons I like and recommend their products.
It starts with a post on https://forum.odroid.com/
First response, within 3 hours is from odroid,
And within 48 hours,
Anyway, see the available triggers by
odroid:~ # cd /sys/class/leds/
odroid:/sys/class/leds # cat blue\:heartbeat/trigger
none nand-disk timer oneshot [heartbeat] gpio cpu0 cpu1 cpu2 cpu3 default-on sd rc-feedback
Configure by echo’ing the desired trigger into trigger. Make it permanent with
odroid:~ # cat > /storage/.config/autostart.sh
echo none > /sys/class/leds/blue\:heartbeat/trigger
^D
This is only for LibreElec 9.1+, now using systemd.
References
https://jbtronics.wordpress.com/2016/05/12/odroid-c2-change-the-function-of-the-blue-led/