This is not a bug
There is no federation between instances as of now. Self hosts cant talk to the main instance, Which is why you get that. it is just not supported. Federation might be planned for the future. there are channels about it in fluxer labs, But It does not currently exist.
So any links you paste from fluxer will not work in a selfhosted instance. as self hosts can only talk to itself. cant talk to fluxer
So no bug, Just not a thing. because selfhosting does not mean auto federation
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Comment by @AvaLilac