Wake on LAN has existed for decades, and works just fine for that if you’ve got an always on machine somewhere on your network. I have Home Assistant set up so that I can hit a button on my phone and it’ll wake my PC from wherever I am and let me connect via Parsec. Once I’m in powering off is fine because I can just tell Windows to shut down.
If you are running Windows try holding shift when you click the shutdown menu item, it’ll force it to do a full power down rather than suspending.
Has existed on decades, just requires the simple process of turning it on in your BIOS, then changing your network adapter advanced settings in Windows to Wake on Magic Packet, and configure the power management settings to "allow this device to wake the computer", etc... It's like a 20 step process.
AFAIK you can't send wol packets between subnets, or over wireguard, without either reconfiguring your router firewall or setting up an proxy service on Lan what you can poke to actually send the wol request.
Wake on LAN requires working suspend, I believe. That's not working, because alas many desktops and workstations don't suspend well these days.
Wake on LAN is my ideal yes & would be perfect for this application. If only suspend werent broken. It's fantastically easy to setup in systems-networkd, a one line WakeOnLan=magic in your .link file. Easy as that for my laptop!
https://wiki.archlinux.org/title/Wake-on-LAN#systemd.link
> Also, you can probably just strap a wifi-capable relay to power pins on your motherboard.
That's a lot more work than just buying a different KVM that already exposes its spare GPIO pins for exactly that purpose. There are plenty of options that come bundled with the necessary cables and adapters to connect the KVM to the motherboard headers while leaving the existing power/reset buttons usable.
Wake on LAN should work from S5 (off), as long as you leave the power supply switched on; but the EU ErP very low standby power setting usually needs to be off.
If you are running Windows try holding shift when you click the shutdown menu item, it’ll force it to do a full power down rather than suspending.