I thought I read that Luigi actually claimed the manifest as his own, but searching around does not bear that out.
Best I can tell, neither the police nor the major media outlets released it in full after the arrest or shortly thereafter, but it was found and shared by this guy later: https://www.kenklippenstein.com/p/luigis-manifesto
Long story short, I still have no clue about the authenticity. One recent headline says Luigi's legal team doesn't want it admissible as evidence for the trial, for what that's worth.
Was that from Bluesky or somewhere else?