This shouldn’t be happening. Upgrading to S2 should take several confirmations in the app. You can reset most S2 devices (except One SL’s)  and add them to an S1 though….

I’ve never seen Sonos “automatically” update to S2. As @106rallye suggests, it has always required an affirmation press in the controller app. 

The latest S1 update has removed all my S2 compatible devices from the S1 platform which now says I should update to S2, But I don’t want to update to S2 - I just want my whole system to work with S1, as it did prior to the latest forced update!

No update is forced. You need to turn off automatic updates in the app and in your app store.

You can reset the speakers that have been upgraded to S2 and add back to your s1 system.as described by other contributors.

Thank you “John B” although one doesn’t have to do updates, you do if you wish to listen to things from your sonos system! I’m sure I’ll be able to sort out the system by resetting everything back to the factory default - one does wonder why sonos have decided to mess with peoples systems AGAIN!!!!

I don't know what has happened here but rubbish to talk  of Sonos deciding to mess with people's systems. It would clearly not be in their own self-interest. 

Do NOT reset everything. Hopefully you don't mean that. You need to leave the devices that are still on S1 as they are.

Really! “  We announced yesterday that some of our oldest Sonos products will be moving into a legacy mode in May of 2020.” though they didn’t say that when I initially bought my system!!

Sigh

Precisely! 

Were you told when the phone, tablet, or computer you’re currently typing on will no longer be supported by the vendor?  Did they tell you this when you bought it?  Did you ask?

Regarding the update of some of your speakers to S2, the likely reason is that you did this accidently, or someone else who has access to your Sonos system upgraded, without realizing what they were doing.  The chance that Sonos did some kind of forceful upgrade to S2 on your system, but not anyone else’s, is extremely unlikely. 

It is literally impossible for Sonos to force an upgrade to S2.  S2 requires you to download and install the S2 app, which Sonos cannot do, it must be done manually by the device user.  

So, no malicious anything at work here.  

My current Linux computer does not have a date when it will be bricked by the software.

As I am the only one with access to my sonos system I doubt that someone else has updated it, I did press the update system on the S1 app (Not update to S2) and then the following happened;

All my S2 compatible devices no longer worked and the app said to update to S2!

However as I didn’t do an update on one of my computers the system will still work from that, however I would still like the whole S1 phone app to control my system…..

The system is the system. The apps are just controllers that show you what is there. What you have just written makes no sense whatsoever. 

Bricked?  I was talking about dropped support. I assume you were as well as your speakers all still work.

Your last statement doesn’t make any sense.  You would need to install the S2 application on your computer in order for you to be able to control your S2 speakers. Also, the controller and speakers need to be on the same software version.  I’m guessing you actually have the S2 app on your phone as well, and did the update there.  Either you didn’t realize it, or you have and don’t want to admit it since you’ve already gone down the road of blaming Sonos.  Either way,  factory reset your S2 speakers, remove the S2 app from every device, and reinstall speakers on S1.

Update;

I’ve just discovered that one of my computers has the S2 version (yes I must have updated to it) so I’m guessing that this is what has caused the problem, thanks Danny (and everyone else) I will try a factory reset on the speakers tomorrow.

Hopefully, that particular speaker is not a Sonos One SL, which can’t be downgraded (for reasons I don’t personally understand), as @106rallye mentioned earlier in the thread. 

Just to make sure. Do not reset the speakers that are still on S1. You need an existing S1 system to be able to reset and add the ones updated to S2.

I did the update yesterday as well and none of my devices are now working either. I am still on S1 OS but nothing works at all. I will need to now go research what is going on as I just did the “Oh Sonos update left click, left click, left click done….” I did not see if there was any information that I needed to know as I usually trust Sonos. I guess now I have to QA them as well in my house. This is just awesome. 

Start by powering off your router and Sonos devices. Power the router back on fully then your Sonos devices. 

Please then post back.