Just a heads up to others; I installed the 15.1 beta this morning on a perfectly functional HomePod and after restarting, it's been completely unable to connect to the Internet.
Any Siri request is met by "I'm having trouble connecting to the Internet" and refers to me to the Home app.
The Home app has no information, and the HomePod has presence on the WiFi network, and the network is functioning fine.
I performed a full device reset, with the red light and all, and after setting it up again, it worked for about 15 minutes before losing Internet again.
Something to do with the beta, clearly, as it was working up until the installation of 15.1. Reported via Feedback, but, wanted to mention here in case others have an issue.