This is about as “official” of a reply as you are going to get:

I also highly doubt adding dark mode to an app is as easy as a 69-word post that probably took less than two minutes to type.

Thanks the official thread.

fyi it’s just a few lines of code. Probably less time than it took you to count the amount of words I’d typed

What’s more of a shame that the requests have been there for it - it’s not hard and it’s not been done. 
 

 That code looks as though it overrides an existing dark mode, not creating light/dark modes for an application.  Regardless, I don’t think lack of knowledge is the reason why there isn’t a dark mode for the app.  I don’t know why the Sonos app doesn’t have modes, but that’s not it.

+1 for his would great to have a dark mode, but I know how slow Sonos can be adding features etc.. so won’t hold out any hope for this.

Hey folks,

Just wanted to let you all know that as of last night Dark Mode is available in the S2 app  There may be some delay in users seeing this update. If you’re not seeing it just yet, you may need to force-quit and reopen the app.

To enable or disable Dark Mode, open the mobile S2 Sonos app and navigate to Settings → App Preferences → Appearance.

Please note, your app and system must be on at least S2 version 13.3 to access this feature.
 

Great. So im guessing system Default means what ever setting you have on the phone the app will change to that appearance.

Exactly. The Sonos app will match whichever option you have enabled for your phone’s UI when set to default 

If I could make another feature request, a Sonos widget, so you can see what's playing, audio format etc etc rather than going into the app.. this would be a great addition.

Not working for android 8 on Huawei M5 tablet.  There is no option for Appearance.