Some motherboards disable power to their ethernet port upon sleep and so WoL will not work.

This is particularly common if the NIC is a power hungry 10GbE port.

However, in the particular case I found, the motherboard also disables oower to any usb GigE adapter attached.

The solution I found was to attach a USB hub with (empty) SD slots and integrated GigE port. As SD cards require power to remain mounted, the motherboard did not shutdown power to this adapter and WoL worked.

There's a "EuP 2013" setting in the BIOS/UEFI. Disable that.

If you use Windows, check in device manager for a setting to allow the device to wake up the computer. (I can't remember the exact name.)

This reminds me of the empty box in a corner of the workshop with the written note "Don't remove!".