Tracked it down a bit: at least the function is not removed, it’s just “complicated”:

When using my Huawei Tablet I can do the following:

Search for artist, open details, select album, see song list: click on the dots beside, a menu pops up, select “more ...”, select Google Play Music => Start radio station

When using my Nokia 8 Sirocco (with the same software version, but a smaller screen naturally), there is NO MORE BUTTON in the menu. To be frank: what the hell? On the smaller screen, the “more”-Button is missing from the menu, but it is there on a bigger screen, where it would be enough space to display a lot more!?

The more button is also available on a Oppo A91 (with a bigger screen obviously).

But, I can still reach this function on my “smaller” Nokia: Start the whole album, go to the playlist, select the dots menu from my selected song: there it is, we have to MORE option again. And there, we have Google Play Music → Start radio station.

So what kind of awful UX decision is this? Please fix it!

Version 12.0
Sonos OS: S2
Build: 58177280
Android: 10 (Model: TA-1005)

P.S.: If it is possible, moving this topic to “software” would be correct now...

Hello @drohhyn,

Welcome to the Sonos Community and thank you for your feedback on our new S2 Sonos app. 

I am glad that you were able to locate the control feature you were looking for and I can pass your experience along to our development team for consideration.

Please don’t hesitate to reach out if you have any further questions or thoughts about using your Sonos system.

The issue itself seems to be fixed, but sometimes is still confusing: there is no indicator in the menu, that you can scroll down below the first 4 items - so maybe a lot of people still do not find this function.

Still can’t find the feature. I’m streaming from Spotify and Amazon music but no luck. 
press the three dots but just get album info, browse artist, add songs to Sonos, add songs to playlist, search for artist or share this song. Nothing more that I can find. 

For amazon the feature is not available, no idea about spotify thou.

Unfortunately GPM is no longer available and the successor youtube music does not have this feature in sonos (but in the own app, which does not work because casting is not possible anymore). So the feature is gone again.