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 trying to do the same today. I think it’s more likely that your instance is blocking access to kbin altogether or specific magazines. For example, I have both a beehaw.org and lemmy.world account. I can access https://beehaw.org/c/[email protected] and can subscribe from that page but https://lemmy.world/c/[email protected] returns a 404: couldnt_find_community error.
The reason I think it might be instance specific versus, say a bug in the server version, is because https://lemmy.ml/c/[email protected] and https://beehaw.org/c/[email protected] both work and but https://lemmy.ml/c/[email protected] doesn’t work. Presumably lemmy.ml is blocking the nsfw magazine.