Someone made a compilation of academic reviews and blogposts here: https://community.signalusers.org/t/wiki-overview-of-third-party-security-audits/13243 but none of them seem to be real security audit reports, ex. compare with real security audits to Delta Chat: https://delta.chat/en/help#security-audits
If you and your contacts are all Android, you can Use Briar. It has no central servers and all traffic go through Tor. Open Source and on Fdroid and recommended by privacyguides.org
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