kbin and lemmy are two different services that interact with the activitypub fediverse. As you mention, they have different standards for linking communities/magazines. There's not really a fix yet. Notably, there's a kbin browser extension to convert ! community names into the proper link.
you can use [link for kbin](/m/[email protected])
and [link for lemmy](/c/[email protected]]
to link a kbin group to kbin users or lemmy users respectively in a way that will work 100% of the time (albeit two separate links). This is what's suggested in lemmy's @newcommunities group.