Wake on LAN can be quite useful for some automations.
But knowing the mac address and typing it in can be a real barrier to entry. Most of the time we are getting into semi expert level for people to know how to find out the mac address of a device.
I had some thoughts on how this could be done as a config flow. This post is a placeholder in case someone wants to pick it up (could be me at a later date!).
ping the broadcast address for the subnet, and wait
ping -b 255.255.255.255 -i5 -c3
look at the arp table
cat /proc/net/arp
Then maybe use host or hostname to find out some network friendly device names if possible.
Then present a dropdown list to the user, allowing them to type the MAC address directly and edit the display name if they wish.