In the home app, go into the HomePod settings and check out “Primary User” in that sub menu, there’s an option to choose “HomePod Account”.

Though I just read this:

This account will only be used on this HomePod and will be allowed to control accessories in this home. This HomePod account will be used when it does not recognise the voice making a music or podcasts request.

Which means that when it recognizes who is using it, it will use that user, otherwise it will use the default, so it’s not exactly what I thought.

you can set your homepods to have a different “user” than yourself so it doesn’t mess with metrics

Mine’s Taylor Swift, Eminem, and Maneskin

you can turn your homepods to be an “alternative” account and not yours so it doesn’t count against your personal plays

my “top” song has 105 plays but I don’t think I’ve ever consciously listened to it and my second highest has like 50 plays and I play that all the time.