Sonos doesn’t add music services, the music service themselves do.  Sonos does work with services to help them integrate, but the initial effort needs to be from them.  You should contact the music service with the following link:

https://docs.sonos.com/docs/how-sonos-works

I don’t think you fully understand the request. I’m asking for Endel to be added a compatible music service just like any other 3rd party service; Apple Music, Spotify, Iheartmusic… 

I assure you, I do fully understand your request.  And as I said, Sonos doesn’t add services.  Content services add themselves by building their integration using the Sonos Music API (SMAPI), testing it, then submitting it to Sonos.  As stated here (https://docs.sonos.com/docs/content-service-get-started):

 

Build

To start an integration:

1. Read about the key requirements of an integration and how Sonos communicates using SOAP requests and responses.
2. Learn how to display content on Sonos.
3. Learn how to playback content on Sonos.
4. Learn how to synchronize your service with Sonos as well as best practices for security and error handling.

To add features and complete your integration, see Adding Content Service Features.

 

Test

Test your service before you submit it to Sonos.

 

Submit

Register your company on the Dev Portal. You’ll use this account to submit your integration to Sonos for validation and release. If you are the first to register for your company, you are responsible for assigning account types for all subsequent accounts associated with your company.

See the Partner account types page for more information.

So if you wish a certain service to be integrated into Sonos, the first step is to contact the service, express your wishes, and send them a link to the above.

Estoy esperando exactamente esto. De hecho, les he contactado (a Endel) hace varios meses pidiéndoles por favor la integración con Sonos. Me respondieron que iban a elevar la solicitud.

Endel doesn’t maintain an official presence here. 
 

Endel no mantiene una presencia oficial aquí.