Mastadon? Lemmy? It would probably have to be standalone so people would’t be turned off from the content from the rest of the fediverse unless there’s a way to prevent federated content from showing on the instance. Just a place to post local news and discussions, maybe a place to sell secondhand. I live near a huge college with a major cs program, so I should be able to get users.
Maybe Lemmy with federation disabled and use a nice 3rd party UI as the default interface for it. If you want to link up with similar community hubs, you can set federation to allow list mode and only federate with each other.