Didn’t see this posted anywhere else, but the Boost is officially dead. It has shuffled off its mortal coil, it is nailed to the perch, etc.
https://support.sonos.com/en-us/article/boost-end-of-sale
It did a fine job for nine years, but SonosNet is clearly getting deprecated and some will have to live with crappy home routers not working correctly causing speakers to vanish from the app randomly.