Deep Linking for the free desktop

what would deep linking (like the android/ios feature) look like for the 
free desktop?

obviously the android/ios feature is explicitly designed to restrict the 
kinds of apps that can be deep link handlers (so e.g. only the official 
twitter app can handle twitter links), which seems very anti-free 
desktop. so what would a free desktop alternative look like?

the point of deep links is that the same link works both in the browser 
and in an app.

also, would it be possible to extend them to, say, atom feeds? those 
traditionally only open in an app, but it'd be neat if they could also 
open in the browser.

(disclaimer: we make fedilinks https://fedilinks.org/ and it is our goal 
to become this, our goal is to be "deep linking for the free desktop". 
but alternative proposals are welcome.)