WoL works as Ethernet¹ broadcast, while Wireguard routes IP, one level above that. So for the purpose of WoL the two ends of the Wireguard tunnel are in two different, not connected networks. In theory you might be able to make it work using subnet directed broadcasts - though creating some means to trigger the WoL packet on where you're terminating your Wireguard might be easier to manage.

Simple option would be just logging in via SSH to trigger it (you could script that - define a host in your SSH client config that just executes a command on connection), or something like a simple web frontend which will then trigger the WoL event.

¹ it is probably fair to assume nowadays that you're using Ethernet, and not something like Token Ring. In case you do it still works the same, just the terminology is different.

If I understand your post correctly, you have 2 PC’s at home: one running wireguard, and one you want to wake using WoL. This is similar to my setup, where I have a server and a personal desktop. When I want to wake my PC remotely, I just ssh to the server and use the server to wake the desktop. Connecting to the server and telling it to wake your PC seems easier than trying to redirect your phone’s WoL app over wireguard.

https://wiki.archlinux.org/title/Wake-on-LAN

You need the Mac address, but the easiest way is to ssh to your rpi and run wol there.

I don't know any wol apps for a phone, but I'm sure they exist.

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

[Thread #143 for this sub, first seen 17th Sep 2023, 17:45] [FAQ] [Full list] [Contact] [Source code]

Can be done with simple port forwarding too