I'm on SDF Lemmy myself. SDF used to have its fair share of outgoing federation issues, and whenever one of my posts wouldn't make it to a non-SDF instance a community is hosted on, I would rant about it in the local SDF venue.
But for the past few months, I really haven't had any issues, save for the occasional post that would never make it across. And today I realized that all of them, without exception, are posts I make to communities hosted on lemmy.world.
Here's the latest one: it shows up on my local SDF Blender@lemmy.world mirror alright but is nowhere to be seen on the primary Blender@lemmy.world community page. It's possible that it will show up there late eventually, I've seen it happen many times on other instances as they synchronize, but if this one is anything like the previous similar problems I've had posting in other lemmy.world-hosted communities, it's basically never going to get there.
So I think there's a very real lemmy.world INCOMING federation issue. In fact, I'm not even sure this very post is going to show up there at all π [EDIT: it looks like this one did]