Wake On Lan (WOL)

Wake On Lan (WOL) is possible on the ASUS M3A78-CM board, but it requires a level of finesse to get it working. First, the cryptically named BIOS option "Power > APM Configuration > Power on From S5 by PMEs" must be enabled. Then, it's important to note that WOL won't work when the power switch is off (i.e. SB_PWR LED is still lit, but the computer has been shut down). Instead, the machine needs to be merely suspended in order to pick up the "magic" WOL ethernet packet. You can suspend it with the command:

sudo systemctl suspend

You'll also need to decide what to do with the BIOS setting "Power > APM Configuration > Restore on AC Power Loss"... [Last State] won't bring it back to suspended after an AC power loss, but it will bring it back to running if the server was running when the power went off. If the power goes out when you're suspended, then you're up a certain creek without a paddle.

On waking, some network drivers need to be reloaded. Check my github's private ubuntu/WOL repository for the script that does this, or follow the steps in this accepted answer: ubuntu 18.04 - ethernet disconnected after suspend

To send a WOL packet, install and run etherwake from some other machine in the same subnet:

sudo apt install etherwake
sudo etherwake -i enp1s0 00:22:15:DE:31:42