Until very recently and still to a degree today, you couldn't host a matrix server that has public registration without someone registering, joining a CSAM room and having all that material replicate to your server.

This would be LESS of a problem if the content was actually encrypted and you as an Admin couldn't access it. But sure, it's not an issue just some bad journalism that's why Matrix just recently actually addressed it (thanks Arathorn for replying): https://matrix.org/blog/2025/02/building-a-safer-matrix/

But if you don't think it's a problem, i'm sure you are willing to link to your publicly open server and let people register, i'll write an e-mail to your local law enforcement to let them know you are knowingly hosting childporn on your server, i'm sure the courts will agree with your opionion