I can't create a broadcast port-forward for remote WOL

Greetings Pickles,

The manuals for the Decos don't seem to be too comprehensive, so I'm unsure if this feature will exist for you, but most modern router firmware has WoL as a separate option in their web UI that lets you put in a MAC/IP of any machine on the local network, and send the magic packet to wake it up.  So instead of forwarding a port, you enable remote web administration mode to log into the router remotely, go to the WoL section, and then wake the PC up from there.  Alternatively, if you can get shell access (Telnet/SSH) to the router, and also be accessible from the outside, then you should be able to log in to that and send the magic packet from that.

But if that doesn't exist or seems unappealing, it's likely the missing piece you're looking for is ARP Binding/Static ARP to be able to get the magic packet to the machine when it's off.  This does appear to be a feature from at least some TP-Link routers, see:

https://www.tp-link.com/ca/support/faq/1536/

In addition, they have an entire article covering WoL with ARP Binding enabled:

https://www.tp-link.com/ca/support/faq/923/#:~:text=Wake%20up%20a%20PC%20on%20WAN%20side

Another workaround is to get a Raspberry Pi and keep that running on your network as a way to get into the LAN from the outside, and send the magic packet out from the Pi.