This post suggests that Kbin magazines can be subscribed to in the same way as Lemmy communities, by searching for them, possibly waiting for one’s instance to pull info about the magazine in, and then visiting the magazine through one’s instance. However, although my home instance is federated with kbin.social, I am not able to get any search results for kbin.social magazines, and it seems that I am not the only one; see here, here, and here, though that last case seems to have fixed itself on its own. The behavior is the same whether I search by URL (e.g., https://kbin.social/m/fediverse), by magazine name with an at-sign (e.g., @fediverse@kbin.social), or by magazine name with a bang (e.g., !fediverse@kbin.social).
I’ve been having this same issue and it just seems to be hit or miss. TBH I think it may be because kbin and even some lemmy servers are getting absolutely hammered right now. Sometimes I can search for a kbin “magazine” on lemmy and it finds it, but most times not.
As I’m writing this, i’m trying to test and kbin is actually down at the moment. I think the reddit wave is just affecting things.
This may be it. kbin.social was outright down a bit earlier, and now I get a captcha page. Perhaps the ActivityPub stuff gets a captcha too, which obviously would break it. I guess I’ll try again another time.