Maybe I'm wrong about this, but didn't the FBI do a lot of digging into GZ's internet activities, in addition to interviewing a lot of people that knew him, and came up with no indication of racism?
My understanding is that only a fraction of the reports generated by the FBI have been included in the discovery.
In the discovery, I don't think there is anything suggesting racism against blacks. There is the social media with negative remarks about 'Mexicans'. There is an interview, I think FDLE, with a former co-worker of GZ's who is of middle eastern background. He said GZ sometimes mocked him with ethnic stereotypes. But I don't think such issues with non-black minorities would be relevant for a federal civil rights prosecution.
Was there some sort of official "we found nothing" statement
I don't think so. Certainly I've never seen such a thing.
I don't think it is the usual practice of the FBI to make such statements. I also don't think the FBI investigation of GZ has been completed.
no indication that the state received anything that they could-- or did-- use in the trial
I wouldn't assume there is identity between what the state could use at trial to suggest hatred, spite, etc., and what the DOJ could use to get into federal court with a civil rights prosecution. The bar might be lower for the latter.
On another site, I've seen the allegation that GZ's on-line fundraising has included some CTH type rhetoric. I can imagine that would be a sufficient hook, if its use is not precluded by its being after-the-fact. I don't know anything about the relevant case law.