They have no data of you to share with the FBI. No list of your contacts, no list of your groups, no data of stickers you use, basically nothing. That’s what’s great about Signal.
I suggest that you read their transparency reports to see what I mean. They share redacted version of their communications with the govts: https://signal.org/bigbrother/santa-clara-county/
It’s about the fact that you HAVE TO trust them to not read your plaintext messages, not see your private photos, whereas Signal is open source (ok both server and client side) and end to end encrypted so you don’t really have to trust anyone.
I’d like to add that Psiphon (which also helps people in countries like mine evade censorship) has also made a similar mechanism. Please help them if you can as well.
SwayWM