The open source client doesn’t mean jack shit dude. Telegram also has open source client. Your data lives on their servers not clients and also, even if the server code is open source, there are many ways for a backdoor and violations of privacy in the infrastructure. When you give up your phone number, there is no privacy.

Matrix is great, you can use another instance though.

https://servers.joinmatrix.org/

Signal is most likely a fed honeypot.

They are super shady, blocked some important security researchers that found a vulnerability from them on all platforms, and they offer no explanation on why using a phone number is MANDATORY for signup.

No reason to trust signal IMO.