Reddit is allowed too. imgur, snap, etc.
I assumed you're fine as long as your raison d'être wasn't porn and the content was user generated / supplied.
0: https://www.theverge.com/2018/11/20/18104366/tumblr-ios-app-...
But perhaps the most catastrophic misfire of all was the notorious ‘porn ban’ that came into place on December 17, 2018 – a policy partly driven by a US law [1] that made websites liable for sex trafficking that might take place on their platform. The ban covers ‘female presenting nipples’, genitals, and any depicted sex acts. Until then, the platform had remained a refuge for a devoted community of users, but this decision affected swift and dire consequences.
(regardless of the content of 18+. Don't know how mobile has had 15 years to do granular content warnings based on decades of other medium but app stores still assume 18+ = porn).
the exact language of their T&Cs?
Not to be too flippant, but we can guess all we want, but the individual apps signed up to specific terms at the time, and you can almost guarantee that Apple (or anyone else) reserves a lot of leeway to themselves as to how they enforce or otherwise police those T&Cs.
All the conjecture in this bit of the thread seems a bit pointless given none of us are reading it, let alone reading the specific bit that whichever app in question might be held to.
Hence my start to it, as well, these seem to be allowed ...
Google Search is different yet, since they aren't the primary host.
On Twitter you can find actual porn straight up.
Why was a perfectly fine Unicode Blackboard X filtered out of my post.
I don't have an iPhone, but I know that you can access it via the official app from Google Play.