is there a federated platform similar to 4chan ie. topic boards with ephemeral linear message threads? i dunno how else to describe it but I like the 4chan format, it’s just got the worst people in the world on there (which I figure could be mitigated by the federated server type thing)
I think there is quite some overlap with Lemmy. You can do images and threads here. And they even show up in a tree-like structure. I’m not sure about ephermal, I don’t think Lemmy is as advanced. But other Fedi software have ephemeral posts.
So, given your requirements, I’d say this is that place. Communities would be your topic boards, and posts would be the threads. And user accounts and moderation would be the improvements to make it less toxic.