tbf people even post born on /biz/, they just eat the ban for it, and even when it isn't outright porn it's often very overtly sexual images. The only thing that makes it browsable is the Wingman browser plugin.
Well /b/ is mostly porn, along with few other boards. Relatively "normal" boards are hosted on 4channel.org domain. That said, 4chan is mostly "shitposting" and memes, don't expect serious discussions.