Overlooked Jovian moons

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It’s sad that books, TV shows, etc always overlook Callisto when talking about people having settlements on Jovian moons.  Basically nobody puts one on Io except as a weird research station which is great, because Io is objectively a terrible place to have to be unless you want to learn more about how hot sulfur behaves in high radiation environments.
Europa is a common one and there are reasons for that.  We can be sure it has a liquid ocean under all that ice, which means there’s a possibility of life.  If you want a colony in a Moon’s ocean that’s an ok place to put it but we think that Ganymede and Callisto also probably have oceans too.  And they have stuff that, like, isn’t water on their surfaces if you want access to other elements for some strange reason.  If you’re not going to put a colony underwater then Europa’s surface is super radioactive and unprotected humans will tend to get a lethal dose after one day on the surface, though under a kilometer of ice you’re fine
Ganymede has lots to recommend it, lots of ice *and* non-ice.  But its radiation is still bad.  Not immediately but you’ll get a yearly dose on the surface 30 times higher than the lowest dose clearly linked to cancer and 60 times higher than the one we let nuclear power plant operators be exposed to.  Enough shielding is very doable, particularly with all that ice around, but you’ll need to spend lots of time indoors.
But Callisto?  On Callisto you get the same dose of background radiation you get within Earth’s protective Van Allen belt.  There are some extra cosmic rays compared to down here in the atmosphere but it’s the same radiation environment the astronauts on the ISS see which seems to be basically fine.  Plus you get the same access to both ice and non-ice you get on Ganymede.  Clearly Callisto is where you make your first space settlement.
Oh, and there are a bunch of other moons but they’re tiny and don’t have enough gravity to make things like cooking or pooping convenient.  We don’t really know how healthy the 1/8 g on the big moons is compared to 0g or 1g so that might make a big health difference too.  Or not, there’s some research on the ISS going on now with animals in centrifuges that might give us a clue in a little while.

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