It sounds simple on the surface. You copy a link on a site into a feed reader app. Then whenever that site updates you get a nice readable article on the app.
But that sounds like something that could be accomplished locally. Why does every RSS reader I run into require an account or otherwise rely on the cloud?
Accounts are needed to sync accross devices. In those cases you‘re not having rss on your device but a server is doing it for you and you simply log in to the server.
If you‘re cool with selfhosting, look into freshrss