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

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.