Just saw a post on reddit alternatives and there was a comment inviting users to laguna.chat. I went and checked it out and the trending communities list included, ‘jews did 911’, ‘killnirs’, ‘hitler was right’, and 'Fuck Nirs’. One of the user accounts was u/HangNi***rs.
Hey Laguna Chat, get your shit together.
Edit: markdown defeated me again. I think you can figure out what those words are.
The short, definitely not legal advice version is that it only becomes a crime if you have actual knowledge that there is CP on your server, and you fail to block access to it and make the legally mandated report.
The law was written with ISPs hosting email and websites for paying customers in mind, but it applies equally well to anonymous user-generated content, federation, and other scenarios we may not have even imagined yet. Being an inattentive server admin is a valid legal defense, though actually having to use it in court would be stressful and expensive.