Hi, hope you’re doing well.
When I looked at the two links, there were two different shortcuts, not sure what happened when you tried to download them.
I don’t have a HomePod to test it out with, so I’m not sure how much I can help you, but this link is to Matthew Cassinelli’s YouTube video on HomePod shortcuts (https://youtu.be/8w7zDk7jmq4)
I believe that this might help you out with what you’re looking to do. I believe from what I remember is that you have to start the shortcut from the HomePod, and then the audio will go to that instead of your iPhone, (or iPad for that matter).
If I think of anything else, I’ll be sure to let you know.