I don't actually use an app as I'm on PC. I often use the search option on kbin to find the local version/link of a magazine or post, so that I can subscribe or comment to anywhere on the social networking Fediverse, from one account.
I actually have two kbin accounts but the 2nd is just a backup in case my usual instance goes down for whatever reason. I also have two Lemmy's (a main and a backup) but I prefer the feel/interface/features of Kbin better, so those are pretty much backup accounts too. Regardless, I don't need them all ... just one, this main account, to browse, subscribe, and comment to other fediverse threads and magazines.
You should be aware that Lemmy uses ! in it's links, while kbin uses @ ... (example !nails@kbin.social compared to @nails@kbin.social) ... sometimes that's all you need to change to find your local version in the search.