Disable the power LED on a Raspberry Pi 4
For so long it didn't even occur to me that you could possibly turn off the power LED on the Pi at all, so it just sat there like an ominous dark glow lighting up the room every night.
Did some digging (my early Google searches revealed everyone has a different way of solving this issue, most of which don't seem to work any more on a newer Pi) and came across this StackOverflow answer.
To summarise, if you want to turn off the LED:
sudo su echo none > /sys/class/leds/led1/trigger
If you want to turn it back on:
sudo su echo default-on > /sys/class/leds/led1/trigger
The only issue I've had so far is that it's not persistent when rebooting, so if anyone has a solution for this, please let me know!
For an older Pi
I haven't checked this myself, but I believe on older Pis you can re-enter the raspi-config and disable the LED's in there. This option is still present on the Pi 4 but once you enter it, you'll get a notice saying it's unavailable.