support ending for ios devices is unacceptable

Pardon me. Where did you see a release from Sonos that they’re going to end support for iOS devices? I use, 99% of the time, iOS devices, such a release from Sonos would be extremely concerning. Can you please provide a link to this statement?

I received a notice that they are ending support for ios17 and earlier. Granted, you can still control playback and streaming from these devices, but no updates or other support. 
The notice was in the app. 
My phone is 16 and iPad is 17. I don’t want to have to buy a new device to be able to have support for this system. 

Are you talking about Sonos not being able to provide new app versions for Apple devices that Apple has ended support for?

Sonos would likely be happy to continue supporting them if you can get Apple to restore the support developers need for new development. 

Same for Google and Android, I have many happily running older app versions as Gooogle ended support for them.

No, just that they are ending support for IOS 17 and older. 

This IOS is only three years old. 

If I’m not mistaken, it’s because, as ​@Stanley_4 says, Apple is ending support for those versions of iOS. If they don’t have access to the documentation from Apple, they can’t fix any bugs. 
 

I’d try to update your devices to a newer version of iOS, if possible, but it’s unlikely that your current version of the controller will stop working, you’ll just be unable to update it, and the firmware on your speakers. Not ideal, but not life ending either. I don’t think Sonos will be turning off your speakers. 

Try these for more details

https://support.sonos.com/en-us/article/sonos-app-requirements

https://support.sonos.com/en-us/article/using-sonos-with-unsupported-operating-systems

Reading iOS 17 Compatibility: Which iPhones get iOS 17, and which don't? | Macworld , your iPhone was introduced before 2017?

For the iPad there’s always the Sonos web app: https://play.sonos.com/nl-nl/web-app

In the above Wiki page, it states quite clearly that iOS 16 and 17 are “Unsupported” (pink color) by Apple.  Are you contending that Sonos should keep supporting iOS versions that Apple themselves no longer support?

That said, I agree a company which not longer supports an operating system a scant 3-4 years after release is one you should consider dropping.  So, when are you ditching Apple? 

But your iOS device is ancient, if it cannot be updated to iOS 18.