Anyone know how this will impact HA users using the Google Cast integration?
Upcoming Speaker Group changes - Google Nest Community
Google to remove Speaker Group volume feature from Nest devices (xda-developers.com)
At this point the only thing I’ve noticed is you can no longer adjust a groups volume.
I was surprised it already hit my system. I noticed it on Friday. 
It should in theory only prevent volume change of the group. I have however been having issue with google groups on and off for months and yesterday found that google group calls did not work at all.
I have now removed the groups from google and made them in home assistant, so at least the group volume adjust not works correctly again, only downside here is when using them for tts they are all slightly out of sync.
But in my head I have taken another little bit of google away and that feels good
I’m guessing by setting up the groups this way you also can’t ask a speaker to play music on a particular group and can only initiate music to the group from HA?
You are correct, we don’t use the speakers for group music anyway so we have lost nothing here, we only use single room and can of course simply ask it to move to another room if required.
We are trying to get away from google as much as possible as it is by far the weakest link in our home.
And at least now for the first time in many months our send tts to groups now works flawlessly
I’ve never been able to get that to work, always getting a response along the lines of “that device does not support that feature”, which is nonsense.
Most of what google assistant does in nonsense from where I am standing, it’s super unreliable and has no consistency what so ever.
Sounds like most of us are in agreement. Google has paid little attention to their Home app, and if anything, the quality, functionality, and reliability has actually DEGRADED over time. Not to get too negative, but my PIxel 5 phone is the worst I’ve ever bought. My Chromecast with Google TV dongle is barely functional, slow, buggy, and doesn’t work with my google assistant nearly as well as my Nvidia ShIeld. My Nest speakers only get my requests right about 50% of the time (used to be closer to 90%) My Google Wifi Mesh system has ridiculous limitations that prevent doing VPNS, or establishing any type of reporting or granular controls. Never adding new functionality, only taking away. Long story short, I am also now making a point of removing every single Google device I have - It might take me a year, but that’s where I’m going.
Woke up this morning and my speaker groups are all messed up. They no longer even appear in the google home app, and if I try and add a new speaker group it says “No devices found” despite the individual speakers showing up normally. This sucks.
Edit: I think removing the existing speakers and re-adding them will let me put them into a group. Have to test it after work, but, at least that seems to be the case.