I have spent 2 frustrating days solving this so I thought I would record my findings. I have 3 computers (2 desktops with the same motherboard/NIC) and an old core2duo laptop all running Mint 19 Mate. On the laptop WOL works fine after enabling it with
and is persistent after shutdowns. The same was not true for the 2 desktops. I tried the procedure as described in the
tutorial but it was not persistent and the "Wake-on:" would always revert to "d" after a shutdown.
After trying numerous methods to solve this I finally found the following
post in this forum. Creating the executable file in /etc/network/if-up.d/ solved the problem. Both computers now start when requested.
I hope this can help someone else