[kevincox]

As far as I am aware WebSub has more or less completely obsoleted RssCloud.

Source: I run a feed reader service that supports WebSub and when I checked none of our subscriptions support RssCloud but not WebSub.

[AndySylvester01]

I would be interested in know what your feed reader service is, and how subscriptions support WebSub.

[kevincox]

My feed reader service is https://feedmail.org. The simplest instructions for WebSub are those on the public Google hub https://pubsubhubbub.appspot.com/. But there are other public hubs available or you can run your own.