Is there an app that allows me to use both Lemmy and Mastodon (and possibly other Fediverse programs?)
Yeah, it seems like being able to follow people is a feature for Lemmy that will arrive at some point as it opens up the Fediverse more but the developers probably have more pressing matters and implementing it might be tricky (I believe kbin is a bit clunky in this regard).
I joined Mastodon last month and so could finally sort of see how it would work - if you were using your Kbin account to log into Mastodon for example you could share a post from a Lemmy community directly to your Mastodon followers.
That is very cool.
The rest is a bit clunky like you say though. I could use my Kbin account to post to Mastodon from this community. Would that serve any purpose? Doesn’t appear so. Might become clearer in the future