We would not recommend Matrix, there are both many fascists on it and they didn’t fix a security vulnerability with their encryption for years that they knew about. Also if you must use Matrix don’t use fluffychat as it doesn’t have the encryption fix yet.
Signal is a better choice for privacy as everything is encrypted by default and it has both the audits and legal testing to prove its safety and code. Something which no other messenger we have seen can honestly say.
Oh dear, another thing to worry about.