If it's just that, you can have a Pi next to it and just ssh in to send a WoL command. Basically nothing to configure.

You can make it simpler to use by making an alias in your shell, or a button on your phone (with one of the countless "ssh button" apps). Or even make a web page for it (some php or python that just calls the WoL function).

OP describes a more transparent (and complex) setup where the Pi presumably acts as a reverse proxy. I'd be curious to know the exact setup too, one of the simplest ways would be to use wake on unicast: https://news.ycombinator.com/item?id=35627107

Other ways include wrapping some scripts around socat, writing your own proxy, systemd socket activation, etc.