Librem Social is not full of porn.
Other Mastodon instances are dedicated to it however, and they show up in search results. (You can see all of Mastodon in search results)
For example, search on “Chicago” and there are a lot of people… advertising their services. Same with Dallas… which is unfortunate, as these are locations I’m interested in, but not in people showing off their assets.
You can moderate the results yourself. Just block a few instances - switter, sinblr, humblr, twimblr, maybe a couple more - and the porn is gone.
I prefer this self-moderation to an instance that decides for me what I can see and what I cannot. You can moderate instances with hate-speech the same way if you wish. And for those that want to see that content, they are free to.
What you do is tap on a person in that instance (domain), tap on the sandwich menu (3 lines), and tap “Block entire domain”
I blocked a few domains (mentioned above), and I never see porn now.