I know Lemmy is about to take off because the porn is quickly moving from drawn henti and furry images to gonewild onlyfan contributors. I call it the QOTP Index (Quality Of The Porn). Reddit is done.
I find porn absolutely disgusting. It's a vile, evil concoction that only caters to the most animalistic of instincts. If you're like me, avoid lemmynsfw.com at all costs.
AFAIK communities are only federated automatically, if someone form your instance is subscribed to the community. Maybe nobody has yet to subscribe to the latter form your instance?
I am all for people enjoying whatever their kink is (as long as it isn’t harming others) but that was one of the first communities I had to block. That group is full of prolific posters.
Your friend may need to go into their profile settings and allow NSFW content. Seems to be off by default. Then your friend will see a range of posts in the all feed.