Wow I didn’t realize that Signal is run on Amazon’s servers and that they contract with the CIA. This article has some interesting points to mitigate the privacy concerns of this real popular service: https://simplifiedprivacy.com/signal-messenger-guide-to-avoid-privacy-mistakes/
Just use Matrix/Element or Session or Briar or Jami or Threema lol
No, use SimpleX.
Matrix but please do not use their identity server. Please.