IE like Crypto AG:
In 2020, it was revealed that the Swiss company, Crypto AG, which provided secure communications services to ~120 governments throughout the 20th century, was secretly ran by the CIA and West German Intelligence. The CIA and later NSA were able to read encrypted communications for many countries such as Saudi Arabia, Iran, Italy, Indonesia, Iraq, Libya, Jordan and South Korea.
Signal is def one, otherwise US government orgs like RFA and OTF wouldn’t be defending and pushing for it so hard in western privacy spaces, nor fund it.
Have a look at Deltachat
Its starting to make headway: FOSS, Decentralised and anyone who is tech inclined can setup their own Relay.