Solution - some homepods not showing up on Apple TV 4k available speaker list
I have several homepods as speakers for an Apple TV 4k, and they would intermittently disappear from the Apple TV speaker list. I recently added Mesh routers to our Xfinity gateway and it turns out that if the gateway is not in bridge mode, a 'double NAT' condition creates two wireless networks and the speakers were switching back and forth. Once I put the gateway in bridge mode, the speakers were all available again.