Signal was literally developed on same place where the NSA headquarters are based and until recently received tens of million dollars from the US government, the founder was a director at Twitter.

This is all public information that you can verify for yourself

There's a reason why only Telegram is accused of hiding terrorists and yet signal never (seldom) gets that kind of newspaper attention.

Never trust someone who worked at Twitter. Always do the opposite of what they say.

On this case: stay with the nostr private messages.