Yes, actually! Liftoff for Lemmy is still in early development, but you can get it on iOS, Android, Windows, and Linux, and it provides precisely this feature. There are a lot of features that Liftoff is yet to incorporate, probably most notably moderator tools and support for adding Kbin accounts – but give it a try regardless, and do what you can to contribute to its further development. Liftoff is an app with a lot of promise and a surprising amount of functionality already this early in its development.

It’s worth noting that Liftoff is a fork of the now abandoned project Lemmur, which I believe was the first Lemmy client to support combining feeds.