Up top, if you hit "Magazines" it gives you a list of magazines on Kbin, sorted by subscriber count. You can find recreations of common Reddit communities here. There's also a search function to look for a particular magazine. These are the ones you mentioned:
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@unexpected (mobile link) - doesn't appear to have a Kbin equivalent yet. Note that because federation is currently off it's not showing all the posts
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@guitar (mobile link) - not learnguitar, but close
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@historymemes (mobile link) - another one without a Kbin equivalent ATM
As for other suggestions, I'm a bit biased. I moderated /r/Disneyland on Reddit, and I've recreated it here on Kbin alongside some of the original mod team: @Disneyland (mobile link). I didn't moderate /r/modeltrains... but I saw there wasn't any model train communities on here, so I decided to create @modeltrains (mobile link).
As far as things I don't moderate, here's a bunch of cool communities I've found here on Kbin. Note that Kbin magazines are case-sensitive (something I'd wish they'd change):
If you see something in here you like but there's no content in it - content comes from users like you!
Be the change you wish to see. Contribute something - anything - to get the community going. If everyone pitches in soon enough communities will start thriving.