I'd have a look at https://lite.koboldai.net/
and start with that. It's free, doesn't need a login and has lots of models available that are run by volunteers. A downside would be occasional wait time and your texts aren't encrypted or anything. Technically everything can be read by server operators.
Easy to use are the paid services. Big and well-known ones include character.ai and poe.com but I'm not sure if they allow NSFW stuff.