@raffles-hogan, as far as I know, there's no way to invoke an Alexa skill or Google Assistant action without saying the wake words like "Alexa" or "Hey Google" first.

About pressing a key - you would have to create the scripts folder and create the script that presses a key. Also, if the computer is actually off, nothing can run on it. I think the post you read was about turning the monitor on.

This page lists all the ways you can trigger commands. I pasted the section that shows the Smart Home and original skills here:

Smart Home voice assistant skills (Example: "Hey Google, turn on calculator")

"TRIGGERcmd Smart Home" Alexa skill "TRIGGERcmd Smart Home" Google Assistant action

Original voice assistant skills (Example: "Alexa, ask TRIGGERcmd to run calculator"):

Alexa skill Google Assistant action