If you’re dedicated to being able to give voice commands to Siri (or perhaps you’re already used to doing that with Alexa), here’s the one-time procedure for being able to use “hey Siri” with a computer that has Mojave installed.
https://www.appleworld.today/blog/2018/12/26/how-to-enable-hey-siri-in-macos-mojave
Abycats' Thoughts 