I was able to get the HomePod to detect the smoke alarm video, but I had to hold the phone speaker right next to the HomePod and it took ~30-60 seconds.
I will have to try with the smoke test button later in the day so I don’t alarm the family.
I also ran around and rebooted all my hubs (ATVs), not just my phone and HomePod. Not sure if that made a difference.
It appears the location based setting for notifications does not work. You have to set it to “off” to get it to work while home. “When I am home” setting did not work for me and I confirmed I have location enabled on my phone. I have some devices with share my location turned off. Not sure if HomeKit is having trouble deciding which device is your primary home vs away location status. Seems like the notification and home vs away should be device specific.
Also, there does not seem to be a way to dismiss the notification in the home app.
I tried checking in, but that just resulted in audio feedback loop between my phone and HomePod. The notification in the home app simply disappears after some period of time.