[theshrike79]

Pretty much all of them? They usually implement the Ye Olde Google Reader API and a few more so that mobile applications can connect in a standard way.

- https://freshrss.github.io/FreshRSS/en/developers/06_Fever_A...

- https://freshrss.github.io/FreshRSS/en/developers/06_GoogleR...

FreshRSS implements two APIs