From what I know, Signal tries to block known bad clients. But guaranteeing such blocks is impossibly hard short of forcing attestations via things like SafetyN

From what I know, Signal tries to block known bad clients. But guaranteeing such blocks is impossibly hard short of forcing attestations via things like SafetyNet that would legitimately impact users as well. There was a case where a teenager in India rose to news media popularity by publishing a messaging app, which was a simple rebranding of Signal he made using some other tool which patches assets iirc. It was blocked by Signal, but only after reports surfacing about it being an insecure rebrand.