Closest thing I know is Fedilab, which works with Mastodon, Pleroma, Pixelfed and Friendica. While compatible with each other, each fediverse service uses different parts and features of ActivityPub (the protocol they all share). It's technically possible to build an app that does it all, but doesn't really sound sensible.
Yeah, it doesn't make much sense to make the app interoperable, when so much effort is spent to make the whole website interoperable, and that allows you to communicate with the rest of the fediverse anyway.
it also sort-of-kind-of-little-bit-of works with Misskey/Calckey. I don't think any official work has been done to enable support, but you can login with your account and browse posts.