I had high hopes on Tox, but now a days I no longer do. Its security status hadn’t change for a while: https://github.com/TokTok/c-toxcore See there:

This is an experimental cryptographic network library. It has not been formally audited by an independent third party that specializes in cryptography or cryptanalysis. Use this library at your own risk.

The underlying crypto library NaCl provides reliable encryption, but the security model has not yet been fully specified. See issue 210 for a discussion on developing a threat model. See other issues for known weaknesses (e.g. issue 426 describes what can happen if your secret key is stolen)

And the 2 issues highlighted there are scary:

https://github.com/TokTok/c-toxcore/issues/210

https://github.com/TokTok/c-toxcore/issues/426

To me experimental, as highlighted in the github repo, is not enough, as mentioned in the 2nd issue.

I really had high hopes on Tox, given its peer-to-peer distributed nature (much better to me than just decentralized by self hosting or so) but I don’t see it improving unfortunately…

Briar is similar, but a 3rd party is just adding support for desktops, and as well as Tox, and I’d guess as any peer-to-peer distributed messaging mechanism, it’s really battery hungry, and phones don’t survive even half a day with them active. I don’t like Briar’s reliance on Tor btw: https://briarproject.org/how-it-works

And on such peer-to-peer distributed systems, it seems really hard to get multi-devices support or syncing. But I’d guess there’s no other choice for some people other than Briar. I’m still looking for a distributed peer-to-peer messenger, not consuming the whole battery at least in a day, and that somehow, through mechanisms like the one keybase uses, allow some sync between devices… But the most important thing of course is battery life… Hopefully supporting as well voice/video calls, and some other common stuff to avoid needing other meesengers to support them…