It seems to federating inward properly now. The predicament that made this easy to overlook is: when S2S connections are initiated outward, that same connection also gets used for inbound traffic from that server too (BiDi).
Meanwhile, if a server wants to talk to chat.wizard.casa, it tries connecting to the S2S port, but can't if the port isn't open. It's only when someone on chat.wizard.casa initiates activity outward that it'd "start working" momentarily. But now that's resolved.
Nonetheless, it's probably a usability bug with Dino worth reporting, if it's burying a more critical error (no S2S connectivity) under a lesser-error (can't discover OMEMO keys, because it can't even talk to the server).