They have reproducible builds on Android if you are that paranoid.
When the military issues secure communications devices, it makes damn sure that BOTH SIDES have a secure device.
What software would not be vulnerable to what you’re describing?
In case you don't trust Google I really suggest OpenSSH or WireGuard, to establish a secure tunnel; and then run IRC, Jabber, SIP, or mumble (as needed) over the tunnel.