Fediverse

Is there such a thing as an application that attempts to talk with the various ActivityPub-implementing tools using their own implementation of ActivityPub?

E.g. you can see posts from Mastadon users as posts, and replies go to the users, and also you can see whole posts from Lemmy communities as posts in the same way, and pop open all the replies if you want to expand the post, and if you reply it, it shows up as a post in Lemmy? I tried subscribing to Lemmy communities from a Mastadon instance, and the implementation definitely isn't ideal.

I'm aware that this is usually not really the right way to approach this problem (basically, ActivityPub should be more strict than it is, so that this happens automatically), but since this is the landscape we have, is there any single app that attempts to navigate it and provide a single good user experience?