There's Pygmalion that looks promising, not on CharacterAI level but they're working on it. And no NSFW filter, whether you run it locally or online. Only issue is, the instructions to run it locally are BS and it took me a lot of fiddling to get is working.

I've been tinkering with ChatFai as well, which seems like a decent alternative; it doesn't seem to have as robust a pre-existing character roster as character.ai (and for that matter it doesn't seem to have a way to search for specific characters, at least not that I've found yet), but you can easily go NSFW with it, especially since it's possible to do completely-private chats with its AI's, so I've gotten some solid results with it for what folks are looking for. The only major drawback is that it's subscription-based; you can use it for free, but only in a fairly limited capacity (memory isn't as good, and you can only send 100 messages a month), and the paid versions that improve on this do get decently-pricey in a hurry.