I'm not knowledgeable enough to argue whether it's fully AI slop, but the main dev has said in the past that they've done work in a private repo, which they then transfer to the main open repo. They also have an LLM usage policy in their repo github.com/fluxerapp/fluxer/bl…, which has

A contributor MUST NOT submit code, prose or media that an LLM has written, rewritten, expanded or completed.

Most of the "12 MILLION lines of code" seems to come from a single week, which to me makes sense in the context of transferring a bunch of completed work over into the public repo. You could maybe still argue that that's just to hide the AI usage. What I can say though is that as a user, the experience is nearly on par with Discord, and not at all as vibe coded as you'd expect.

For self-hosting, they've said they're working on federation, and even announced the protocol they plan to use (polyproto).

I say this as a Matrix user myself, but Matrix is never going to be able to compete with Discord until they get a client that's similar to Discord, available on all platforms. Sable is close, but their iOS app needs to be sideloaded, which is unfortunately a dealbreaker for many non-techy people. #Fluxer