Continuing on my series of how the heck do I play something to my expensive HomePod speakers... You can use an app to AirPlay most any audio to your HomePod with a Line-Level 3.5mm Audio Input Adapter Cable. Video evidence is here.
Here is a little menu bar app to make it easier to set a star rating on the currently playing iTunes track. I made this because I use star ratings heavily to organize my music, and have a lot of tracks without ratings.