Thanks, I will try to find some time and join your team and help with development. I lost hopes in tox despite being much more mature than matrix.
Depends on your definition of mature. The security was mature, but the UX was always garbage and there was never consensus in the ecosystem and huge swathes of critical features (like usable dns) have never been wholly adopted.
Matrix is lacking its E2E encryption but already has everything else. You can use Vector today to replace Hangouts or Skype completely.
The documents I know of that provide details about it are here:
* https://matrix.org/jira/browse/SPEC-162 (the tracking issue for the feature in Matrix's issue tracker)
* https://matrix.org/git/olm (C implementation of the protocol formerly known as axolotl v2 developed for use in Matrix)
* https://matrix.org/speculator/spec/drafts%2Fe2e/client_serve... (draft of the spec for E2E)