I'm gonna miss /rg/ and my Doom and Quake bros.

That community even had custom map contests.

Please, just let it die.

There's a project called FChannel that implements ActivityPub, but I honestly don't see the point. What would federation add to the chan experience? The boards on 4chan were almost separate websites anyway. There are no accounts. There is no interaction across threads. The only shared part is the UI. So you could achieve basically the same thing if everyone hosted a single board with vichan.