There are a few, but they’re usually defederated. Lots of weird porn on the remaining ones that isn’t acceptable even with the tags and auto blurring enabled.

Hosting images and video is really expensive. That’s why large Lemmy instances often lower the file size limit for media uploaded to them. Combine that with the moderation pressure NSFW content requires, and you’re left with very few options.

If you’re willing to do the moderation and think you can keep abuse to a minimum, you’re free to set one up yourself. You can learn to set up a server or rent server space with various companies dedicated to Mastodon. Do make sure you read up on laws regarding child abuse material, though, and make sure you know what IP ranges to ban if you live in a country with laws regarding porn access or are within legal reach of one (China, the UK, the USA). Also make sure to be ready to moderate kinky shit people will upload (including, but not limited to, rape role play, stuff involving various types of bodily fluids, gore, stuff involving real or imaginary animals) and make sure you have a list of what you do and don’t allow so you can block and ban without hesitation.

I wouldn’t want to run a server like that. The folks are lemmynsfw seem to be willing, so maybe take a peek at the rules and moderation style there if you’re planning on hosting something like that.