[lrvick]

End to end encryption is only useful when the software on each end is open source and deterministically built/distributed by third parties with accountability.

Even Signal or Google/Apple could ship a bad Signal app update to targeted devices to dump convos if ordered. If you use Matrix with a client from an F-Droid build or a reproducible build from debian etc, then the Matrix developers literally could not comply with orders to obtain your plaintext content.