lemm.ee itself also doesn't allow porn but that's a "don't post it with your lemm.ee account" type of rule. I think it also gets filtered out of the all feed, but you can definitely subscribe to stuff over on lemmynsfw.com. Long story short porn is a bugger to mod and the legal situation when hosting (and uploading an image with a lemm.ee account would imply that) is never trivial, either.

Somewhat relatedly, image upload limits are also rather strict, 100kb, to avoid that becoming a resource hog.