Answering my own question, I have found this, is it any good ? https://apps.apple.com/se/app/soro-for-sonos/id1550457805?platform=iphone

Or any other to recommend ? 

So, how do you figure we won’t get iPhone / iOS lock screen controls back to the Sonos app? It has basically never worked for me, but I really could use them. Also, it’s a pretty standard feature of any streaming app, right? I never understood why Sonos couldn’t make this work somehow.

Was hoping this new release would at least give us that, but seems not…

Thanks!

That’s the whole point, Sonos isn’t a streaming app.  No music actually gets played by the app, or the device the app is loaded on.  In reality, the app is just a remote control, all streaming takes place on the Sonos hardware.  Since Apple does not allow you to control 3rd party hardware via the lock screen or hard button controls, Sonos figured out a hack (that, as you found, sometimes worked, sometimes didn’t) that tricked iOS into thinking the app was a streaming app by playing a silent track in the background.  Apple recently cracked down on this hack, threatening to remove the Sonos app from the App Store if Sonos didn’t remove the lock screen and hard button controls. 

Aha, got it. Apple’s rules makes no sense in many cases.

Thanks @jgatie !