This wasn't a voluntary update from Sonos. One could not opt out. It was a change in their entire infrastructure and a redesign of the app on the app store. It broke whether you updated the app on your phone and/or the firmware on your speakers or not. Unless you had a single speaker or were very lucky to have a network setup exactly like they had in their "test" labs (if they actually did any testing), you were affected -- regardless of what system versions your equipment was running.
Some Android users who had saved a copy of the old app's .apk file were able to get some functionality back by sideloading it, but that's not something that was applicable to iOS/iPadOS. The Mac app was able to at least do things like getting a speaker to stop playing when the iPhone app would no longer communicate with the Sonos servers or speakers. People had speakers spontaneously turn itself to volume 0 or volume 100. Play commands were sometimes delayed by hours, starting in the middle of the night long after people gave up trying to get it to work (nice surprise to wake up to). People would start a stream then literally lose control of it, necessitating physically unplugging the speaker from the AC just to get it to stop. Some had entire multiroom speaker systems simply disappear from their app and account, requiring multiple hard resets of all their gear and redoing all of their room assignments from scratch, if they could even get them to connect at all. Some people, like me, had trouble getting the speakers to actually produce any sound (app looked like it was playing... but speaker(s) remained silent or would repeatedly drop the stream for 10-15 seconds at a time). For whatever brilliant reason, they decided that all speaker control needed to go from your phone, up to their servers -- including for things like volume changes -- then back down to your speakers, instead of just controlling everything locally like it used to. And the latency was measured sometimes in minutes, not milliseconds.
It was literally months before Sonos actually admitted there was a problem (and would just blame users' wifi systems for the trouble). Then the CEO wrote a half-assed letter of apology and sent it to all their registered users taking the blame for the lack of testing and even rehired all (or many) of the engineers they laid off to come back and fix the app, including the architect of the original Sonos app.
The new app still doesn't have feature parity with the old one, but at least the Sonos system works now.
