I know you can watch kbin posts. Very easily. Just treat it as if it were any other instance. Say there’s a community called water in kbin (there probably isn’t), you could access it by going to lemmy.ml/[email protected]

That’s it.

For mastodon, though, no idea. I’m too new. I do know that kbin can access mastodon stuff and it has a micro blogging mode. Haven’t seen any such thing on lemmy yet.